Writing Formulas with Rich Text Areas

Questions
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15

The trigger? Maybe something like this:

trigger yourTriggerName on YourObjectAPI_Name (before insert, before update) {

List <YourObjectAPI_Name> triggerSet = Trigger.new;
for ( YourObjectAPI_Name theRow : triggerSet )
{
    Integer n = 0;

    if ( String.isEmpty(theRow.Salesforce_Enrollments__c) ) { n++; }
    if ( String.isEmpty(theRow.Total_Referrals__c) ) { n++; }
    ...
    if ( String.isEmpty(theRow.Retention_Explanation__c) ) { n++; }
    
    //if ( n > 0 )
    //{
        theRow.YourNumericField__c = n/7; //assuming 7 fields to test
    //}
}

}

(The field you add to the object (Your Numeric Field) is a Number datatype, not a Formula.)