I have a VF page that our sales people use to add and configure products to their Opportunities. I've added some Javascript to allow them to run pricing scenarios in real-time without having to save to the database. This is working perfectly.  In addition, we have a requirement that any time someone adds a "Support" product to an Opportunity, the Quantity is automatically calculated by totaling the Quantity of any Products from the Product Family called "MTP."  

To accomplish this, I added a method to my controller and used an apex:actionsupport tag to refresh the quantity when an MTP product Quantity is set or updated. It's almost working correctly, but it seems to be double-counting the quantity from the MTP Products, and I can't figure out why. Any suggestions would be very much appreciated. Cheers!

Screen Shot:


Relevant Controller Method:

public PageReference calculateSupport(){
        Decimal supportQuantity;
        supportQuantity = 0;
        for(OpportunityLineItem soli : supportShoppingCart){
            if(supportQuantity!=null){
                supportQuantity+=soli.Quantity;
            }
        }
        for(OpportunityLineItem oli : shoppingCart){
            if(oli.PriceBookEntry.Product2.Type__c=='Support'){
                oli.Quantity=supportQuantity;
            }
        }
        return null;        
    }

Relevant VF Code:

<!--********** Quantity **********-->
                    <apex:column headerValue="{!$ObjectType.OpportunityLineItem.Fields.Quantity.Label}">
                        <apex:inputField value="{!s.Quantity}" id="quant" style="width:70px" required="true" rendered="{!IF(s.PriceBookEntry.Product2.Type__c == 'Support',False, True)}">
                            <apex:actionSupport event="onchange" reRender="tot"/>
                            <apex:actionSupport event="onchange" action="{!calculateSupport}"/>
                        </apex:inputField>
                        <apex:outputText id="quantreadonly" value="{!s.Quantity}" rendered="{!IF(s.PriceBookEntry.Product2.Type__c == 'Support',True, False)}"/>
                    </apex:column>

Entire Controller:

public with sharing class opportunityProductEntryExtension {

    public Opportunity theOpp {get;set;} 
    public String searchString {get;set;}
    public OpportunityLineItem[] shoppingCart {get;set;}
    public OpportunityLineItem[] supportShoppingCart {get;set;}     
    public PriceBookEntry[] AvailableProducts {get;set;}
    public Pricebook2 theBook {get;set;}   
    public String toSelect {get; set;}
    public String toUnselect {get; set;}
    public Decimal Total {get;set;}   
    public Boolean overLimit {get;set;}
    public Boolean multipleCurrencies {get; set;} 
    private Boolean forcePricebookSelection = false;
    
    private opportunityLineItem[] forDeletion = new opportunityLineItem[]{};


    public opportunityProductEntryExtension(ApexPages.StandardController controller) {

        // Need to know if org has multiple currencies enabled
        multipleCurrencies = UserInfo.isMultiCurrencyOrganization();

        // Get information about the Opportunity being worked on
        if(multipleCurrencies)
            theOpp = database.query('select Id, Pricebook2Id, Pricebook2.Name, CurrencyIsoCode from Opportunity where Id = \'' + controller.getRecord().Id + '\' limit 1');
        else
            theOpp = [select Id, Pricebook2Id, PriceBook2.Name from Opportunity where Id = :controller.getRecord().Id limit 1];
        
        // If products were previously selected need to put them in the "selected products" section to start with
        shoppingCart = [select Id, Quantity, TotalPrice, UnitPrice, Description, List_Price__c, Disti_Transfer_Price2__c, Disti_Transfer_Price__c, PriceBookEntryId, PriceBookEntry.Name, PriceBookEntry.UnitPrice, PriceBookEntry.IsActive, PriceBookEntry.Product2Id, PriceBookEntry.Product2.Name, PriceBookEntry.Product2.Product_Term_Years__c, PriceBookEntry.PriceBook2Id, PriceBookEntry.Product2.SKU__c, PriceBookEntry.Product2.Family, PriceBookEntry.Product2.Type__c, Service_Term_in_Months__c, PriceBookEntry.Disti_Transfer_Price__c, Discount_off_list_manual__c from opportunityLineItem where OpportunityId=:theOpp.Id];
        supportShoppingCart = [select Id, Quantity, TotalPrice, UnitPrice, Description, List_Price__c, Disti_Transfer_Price2__c, Disti_Transfer_Price__c, PriceBookEntryId, PriceBookEntry.Name, PriceBookEntry.UnitPrice, PriceBookEntry.IsActive, PriceBookEntry.Product2Id, PriceBookEntry.Product2.Name, PriceBookEntry.Product2.Product_Term_Years__c, PriceBookEntry.PriceBook2Id, PriceBookEntry.Product2.SKU__c, PriceBookEntry.Product2.Family, PriceBookEntry.Product2.Type__c, Service_Term_in_Months__c, PriceBookEntry.Disti_Transfer_Price__c, Discount_off_list_manual__c 
                                from opportunityLineItem 
                                where OpportunityId=:theOpp.Id AND PriceBookEntry.Product2.Family=:'MTP' AND PricebookEntry.Product2.Type__c=:'Subscription'];        
        // Check if Opp has a pricebook associated yet
        if(theOpp.Pricebook2Id == null){
            Pricebook2[] activepbs = [select Id, Name from Pricebook2 where isActive = true limit 2];
            if(activepbs.size() == 2){
                forcePricebookSelection = true;
                theBook = new Pricebook2();
            }
            else{
                theBook = activepbs[0];
            }
        }
        else{
            theBook = theOpp.Pricebook2;
        }
        
        if(!forcePricebookSelection)
            updateAvailableList();
    }
    
    // this is the 'action' method on the page
    public PageReference priceBookCheck(){
    
        // if the user needs to select a pricebook before we proceed we send them to standard pricebook selection screen
        if(forcePricebookSelection){        
            return changePricebook();
        }
        else{
        
            //if there is only one active pricebook we go with it and save the opp
            if(theOpp.pricebook2Id != theBook.Id){
                try{
                    theOpp.Pricebook2Id = theBook.Id;
                    update(theOpp);
                }
                catch(Exception e){
                    ApexPages.addMessages(e);
                }
            }
            
            return null;
        }
    }
       
    public String getChosenCurrency(){
    
        if(multipleCurrencies)
            return (String)theOpp.get('CurrencyIsoCode');
        else
            return '';
    }

    public void updateAvailableList() {
    
        // We dynamically build a query string and exclude items already in the shopping cart
        String qString = 'select Id, Name, Pricebook2.Name, Pricebook2Id, IsActive, Product2.Name, Product2.Family, Product2.Type__c, Product2.IsActive, Product2.Description, UnitPrice, Product2.SKU__c, Disti_Transfer_Price__c, Product2.Product_Term_Years__c, Product2.SKU_Level_Discount__c from PricebookEntry where IsActive=true and Pricebook2Id = \'' + theBook.Id + '\'';
        if(multipleCurrencies)
            qstring += ' and CurrencyIsoCode = \'' + theOpp.get('currencyIsoCode') + '\'';
        
        // note that we are looking for the search string entered by the user in the name OR description
        // modify this to search other fields if desired
        if(searchString!=null){
            qString+= ' and (Product2.Name like \'%' + searchString + '%\' or Product2.Description like \'%' + searchString + '%\')';
        }
        
        Set<Id> selectedEntries = new Set<Id>();
        for(opportunityLineItem d:shoppingCart){
            selectedEntries.add(d.PricebookEntryId);
        }
        
        if(selectedEntries.size()>0){
            String tempFilter = ' and Id not in (';
            for(Id i : selectedEntries){
                tempFilter+= '\'' + (String)i + '\',';
            }
            String extraFilter = tempFilter.substring(0,tempFilter.length()-1);
            extraFilter+= ')';
            
            qString+= extraFilter;
        }
        
        qString+= ' order by Product2.Name';
        qString+= ' limit 101';
        
        system.debug('qString:' +qString);        
        AvailableProducts = database.query(qString);
        
        // We only display up to 100 results... if there are more than we let the user know (see vf page)
        if(AvailableProducts.size()==101){
            AvailableProducts.remove(100);
            overLimit = true;
        }
        else{
            overLimit=false;
        }
    }
    
    public void addToShoppingCart(){
    
        // This function runs when a user hits "select" button next to a product
        list<Price_Book_Discounts__c> discounts = [SELECT Discount__c, Name
                                                   FROM Price_Book_Discounts__c 
                                                   WHERE Name =: theBook.Name];
        list<SKU_Discounts__c> skus = [SELECT Discount__c, SKU__c, Price_Book_Name__c
                                           FROM SKU_Discounts__c 
                                           WHERE Price_Book_Name__c =: theBook.Name];
        list<Product2> products = [SELECT Product_Term_Years__c, Name FROM Product2];                                                                           
        Map<String, Decimal> pbNameToDiscountMap =  new Map<String, Decimal>();
		Map<String, Decimal> skuToDiscountMap = new Map<String, Decimal>();
        Map<Decimal, Decimal> yearsToMonthsMap = new Map<Decimal, Decimal>();
        for(Price_Book_Discounts__c discount : discounts){
            pbNameToDiscountMap.put(discount.Name, discount.Discount__c);
        }
        for(SKU_Discounts__c sku : skus){
            if (!SkuToDiscountMap.containsKey(sku.SKU__c)) {
                SkuToDiscountMap.put(sku.SKU__c, sku.Discount__c);
            } 
        }
        for(Product2 prod : products){
            if(!yearsToMonthsMap.containsKey(prod.Product_Term_Years__c)){
                if(prod.Product_Term_Years__c == null){
                    yearsToMonthsMap.put(prod.Product_Term_Years__c, 12);
                }
                if(prod.Product_Term_Years__c == 1){
                    yearsToMonthsMap.put(prod.Product_Term_Years__c, 12);
                }
                if(prod.Product_Term_Years__c == 3){
                    yearsToMonthsMap.put(prod.Product_Term_Years__c, 36);
                }
            }
        } 
        for(PricebookEntry d : AvailableProducts){             
            if((String)d.Id==toSelect && d.Product2.Name.contains('Support')){
                shoppingCart.add(new opportunityLineItem(OpportunityId=theOpp.Id, PriceBookEntry=d, PriceBookEntryId=d.Id, Quantity=0, Service_Term_in_Months__c = yearsToMonthsMap.get(d.Product2.Product_Term_Years__c), UnitPrice=d.UnitPrice, Discount_off_list_manual__c = 12));
                break;
            }
            if((String)d.Id==toSelect && d.UnitPrice<>0 && !d.Product2.Name.contains('Support')){
                if(d.Product2.SKU_Level_Discount__c == false){
                    shoppingCart.add(new opportunityLineItem(OpportunityId=theOpp.Id, PriceBookEntry=d, PriceBookEntryId=d.Id, Quantity=0, Service_Term_in_Months__c = yearsToMonthsMap.get(d.Product2.Product_Term_Years__c), UnitPrice=d.UnitPrice, Discount_off_list_manual__c = pbNameToDiscountMap.get(theBook.Name)));
                    break;                    
                }
                if(d.Product2.SKU_Level_Discount__c == true){
                    shoppingCart.add(new opportunityLineItem(OpportunityId=theOpp.Id, PriceBookEntry=d, PriceBookEntryId=d.Id, Quantity=0, Service_Term_in_Months__c = yearsToMonthsMap.get(d.Product2.Product_Term_Years__c), UnitPrice=d.UnitPrice, Discount_off_list_manual__c = SkuToDiscountMap.get(d.Product2.SKU__c)));
                    break;                    
                }                
            }     
            if((String)d.Id==toSelect && d.UnitPrice==0){
                if(d.Product2.Name.contains('Evaluation')){
                    shoppingCart.add(new opportunityLineItem(OpportunityId=theOpp.Id, PriceBookEntry=d, PriceBookEntryId=d.Id, Quantity=0, Service_Term_in_Months__c = 2, UnitPrice=d.UnitPrice, Discount_off_list_manual__c = 0));
                    break;
                }else{
                    shoppingCart.add(new opportunityLineItem(OpportunityId=theOpp.Id, PriceBookEntry=d, PriceBookEntryId=d.Id, Quantity=0, Service_Term_in_Months__c = yearsToMonthsMap.get(d.Product2.Product_Term_Years__c), UnitPrice=d.UnitPrice, Discount_off_list_manual__c = 0));
                    break;
                }
            }            
        }
        for(OpportunityLineItem soli : shoppingCart){
            if(soli.PriceBookEntry.Product2.Type__c=='Subscription' && soli.PriceBookEntry.Product2.Family=='MTP'){       
                supportShoppingCart.add(soli);
            }
        }
        updateAvailableList();    
    }

    public PageReference calculateSupport(){
        Decimal supportQuantity;
        supportQuantity = 0;
        for(OpportunityLineItem soli : supportShoppingCart){
            if(supportQuantity!=null){
                supportQuantity+=soli.Quantity;
            }
        }
        for(OpportunityLineItem oli : shoppingCart){
            if(oli.PriceBookEntry.Product2.Type__c=='Support'){
                oli.Quantity=supportQuantity;
            }
        }
        return null;        
    }

    public PageReference removeFromShoppingCart(){
    
        // This function runs when a user hits "remove" on an item in the "Selected Products" section
    
        Integer count = 0;
    
        for(opportunityLineItem d : shoppingCart){
            if((String)d.PriceBookEntryId==toUnselect){
            
                if(d.Id!=null)
                    forDeletion.add(d);
            
                shoppingCart.remove(count);
                break;
            }
            count++;
        }
        
        updateAvailableList();
        
        return null;
    }
    
    public PageReference onSave(){
    
        // If previously selected products are now removed, we need to delete them
        if(forDeletion.size()>0)
            delete(forDeletion);
    
        // Previously selected products may have new quantities and amounts, and we may have new products listed, so we use upsert here
        try{
            if(shoppingCart.size()>0)
                upsert(shoppingCart);
        }
        catch(Exception e){
            ApexPages.addMessages(e);
            return null;
        }  
           
        // After save return the user to the Opportunity
        return new PageReference('/' + ApexPages.currentPage().getParameters().get('Id'));
    }
    
    public PageReference onCancel(){
 
        // If user hits cancel we commit no changes and return them to the Opportunity   
        return new PageReference('/' + ApexPages.currentPage().getParameters().get('Id'));
    }
    
    public PageReference changePricebook(){
    
        // This simply returns a PageReference to the standard Pricebook selection screen
        // Note that is uses retURL parameter to make sure the user is sent back after they choose
    
        PageReference ref = new PageReference('/oppitm/choosepricebook.jsp');
        ref.getParameters().put('id',theOpp.Id);
        ref.getParameters().put('retURL','/apex/opportunityProductEntry?id=' + theOpp.Id);
        
        return ref;
    }
}