Bhanu,

The coding worked perfectly! I am so appreciate it of you for your coding! I spent all morning researching the code and I actually understood some parts of the coding. Obviously I will have to do more studying. I will be taking a beginner's course in Java soon. 

I used the same structure of coding you created for a similar situation, view below 


Settlement__c  (custom object)

• Recovery_Total__c  - Formula (Currency) field with formula -  Initial_Value__c - Book_Value__c
• Deal__c - Lookup(Opportunity)

Opportunity

• Settlement_Recovery_Total__c - Currency(16, 2) field

trigger UpdateToRecoveryTotalOnOpportunity on Settlement__c (after insert,after update,after delete){
    Set<Id> oppIds = new Set<Id>();
    List<Opportunity> lstOppToBeUpdated = new List<Opportunity>();
   
    if(Trigger.isAfter){
        if(Trigger.isInsert || Trigger.isUpdate){
            for(Settlement__c settlement : trigger.new){
                if(Trigger.isInsert){
                    oppIds.add(settlement.Deal__c);
                }
                else if(Trigger.isUpdate){
                    if(settlement.Reovery_Total__c != trigger.OldMap.get(matter.Id).Reovery_Total__c){
                            oppIds.add(settlement.Deal__c);
                    }
                }
            }
        }
        if(Trigger.isDelete){
                for(Settlement__c settlement : trigger.old){
                    oppIds.add(settlement.Deal__c);
                }
        }
    }
    if(!oppIds.isEmpty()){
        for(Opportunity opp :[SELECT Id,Settlement_Recovery_Total__c,(SELECT Id,Recovery_Total__c FROM Settlements__r) FROM Opportunity WHERE Id IN :oppIds]){
                    Decimal RecoveryTotal = 0;
                    for(Settlement__c matter : opp.Settlements__r){
                            if(settlement.Recovery_Total__c!= null){
                                RecoveryTotal = RecoveryTotal + settlement.Recovery_Total__c;
                            }
                    }
                    opp.Settlement_Recovery_Total__c = RecoveryTotal;
                    lstOppToBeUpdated.add(opp);
        }
        if(!lstOppToBeUpdated.isEmpty()){
            update lstOppToBeUpdated;
        }
    }
}


Question - can Apex Triggers recognize Formula (Currency) fields in an Object? the reason for my question is because I received an error message below. 

Error: Compile Error: Variable does not exist: settlement.Recovery_Total__c at line 29 column 65

Which is this line code below within the Settlement__c object 

RecoveryTotal = RecoveryTotal + settlement.Recovery_Total__c;

I really appreciate your time, I have learned a lot from your assistance.