I am trying to edit this code so that it updates the field if the contact role = Billin Contact and it does not have to be primary (I do not care about the promary contact only about having a billing contact) the trigger is working with a validation rule that checks if a primary contact has been added so I assume it can be tweak to be based on billing contact instead.... right? 


trigger updatecontactrolecount on Opportunity (before insert, before update)
{

Boolean isPrimary;
Integer iCount;

Map<String, Opportunity> oppty_con = new Map<String, Opportunity>();//check if the contact role is needed and add it to the oppty_con map
for (Integer i = 0; i < Trigger.new.size(); i++) 
{
        oppty_con.put(Trigger.new[i].id,
        Trigger.new[i]);      
}
isPrimary = False; 
for (List<OpportunityContactRole> oppcntctrle :[select OpportunityId from OpportunityContactRole where (OpportunityContactRole.IsPrimary = True and OpportunityContactRole.OpportunityId in :oppty_con.keySet())])
{
 if (oppcntctrle .Size() >0)
 {
 isPrimary = True;     
 }
}
iCount = 0;
for (List<OpportunityContactRole> oppcntctrle2 : [select OpportunityId from OpportunityContactRole where (OpportunityContactRole.OpportunityId in :oppty_con.keySet())])//Query for Contact Roles
{    
 if (oppcntctrle2 .Size()>0)
 {
 iCount= oppcntctrle2 .Size();     
 }
}
for (Opportunity Oppty : system.trigger.new) //Check if  roles exist in the map or contact role isn't required 
{
Oppty.Number_of_Contacts_Roles_Assigned__c = iCount;
Oppty.Primary_Contact_Assigned__c =isPrimary; 
}
}