Hi all, 
I'm looking to update a picklist on a visualforce page, based on the values from a text formula field. 

Visualforce Page: 
 

<apex:page standardController="Scorecard__c" extensions="ScorecardExtension" lightningStylesheets="true">
    <apex:form >
        <apex:pageBlock title="Scorecard" mode="edit">
            <apex:pageBlockButtons >
                <apex:commandButton action="{!save}" value="Calculate"/>
            </apex:pageBlockButtons>
            <apex:pageBlockSection columns="2">
                <apex:outputField value="{!Scorecard__c.Name}"/>
                <apex:outputText value=""/>
                <apex:outputField value="{!Scorecard__c.Revenue_M__c}"/>
                <apex:outputText value=""/>
                <apex:inputField value="{!Scorecard__c.Revenue__c}"/>
                <li Style="list-style:none">{!Scorecard__c.Calculate_Revenue__c}/150</li>
                <apex:outputField value="{!Scorecard__c.Full_NAICS_Codes__c}"/>
                <apex:outputText value=""/>
                <apex:inputField value="{!Scorecard__c.Industry__c}"/>
                <li Style="list-style:none">{!Scorecard__c.Calc_Industry__c}/100</li>
                <apex:inputField value="{!Scorecard__c.Sourcing_Frequency__c}"/>
                <li Style="list-style:none">{!Scorecard__c.Calc_Sourcing_Frequency__c}/100</li>
                <apex:inputField value="{!Scorecard__c.Role__c}"/>
                <li Style="list-style:none">{!Scorecard__c.Calc_Job_Function_Pick__c}/100</li>
                <apex:inputField value="{!Scorecard__c.Sourcing_Type__c}"/>
                <li Style="list-style:none">{!Scorecard__c.Calc_Sourcing_Type__c}/100</li>
                <apex:inputField value="{!Scorecard__c.Opportunity_Size__c}"/>
                <li Style="list-style:none">{!Scorecard__c.Cal_Opportunity_Size__c}/100</li>
                <apex:inputField value="{!Scorecard__c.Target_Pricing__c}"/>
                <li Style="list-style:none">{!Scorecard__c.Calc_Target_Pricing__c}/40</li>
                <apex:inputField value="{!Scorecard__c.Manufacturing_Processes__c}"/>
                <li Style="list-style:none">{!Scorecard__c.Calc_Manufacturing_Process__c}/50</li>
                <apex:inputField value="{!Scorecard__c.Customer_Responsiveness__c}"/>
                <li Style="list-style:none">{!Scorecard__c.Calc_Customer_Responsiveness__c}/85</li>
               <li Style="list-style:none"><apex:outputField value="{!Scorecard__c.Score__c}"/>{!Scorecard__c.Score__c}/825</li>
             </apex:pageBlockSection>
        </apex:pageBlock>
    </apex:form>
</apex:page>

If Revenue_M__c is populated, I want to update the Revenue__c field accordingly. I've started a controller extension, but don't know if that's the right way to go. 

public class ScorecardExtension {
 
    private final Scorecard__c sccard;
    
    public ScorecardExtension(ApexPages.StandardController stdController) {
        this.sccard = (Scorecard__c)stdController.getRecord();
    }
    
    public String getRevenue() {
         switch on this.sccard.Revenue_M__c {
            when '<10' {	
                this.sccard.Revenue__c = '<$5m (or no size on Zoominfo)';
            }	
            when '11-25' {		
                this.sccard.Revenue__c = '$5-250m';
            }
            when '26-50' {	
                this.sccard.Revenue__c = '$5-250m';
            }
            when '51-250' {	
                this.sccard.Revenue__c = '$5-250m';
            } 
            when '251-500' {	
                this.sccard.Revenue__c = '$250m+';
            } 
            when '501-2,500' {	
                this.sccard.Revenue__c = '$250m+';
            } 
            when '2,501-5,000' {	
                this.sccard.Revenue__c = '$250m+';
            }
            when '5,000+' {	
                this.sccard.Revenue__c = '$250m+';
            } 
            when else {		
                this.sccard.Revenue__c = 'None';
            }
        }
    
        return this.sccard.Revenue__c;
    }
}