All,

I have a custom object Matter__c  label is Engagement with a lookup relationship field Deal__c  datatype Lookup(Opportunity) that connects to Opportunity. Opportunities object in my Salesforce database is rename to Deal__c  .
 
I am requesting if the currency value in the custom currency (16,2)  field Total_Fees__c in the custom object  Matter__c which may contain one or more records ,  will Rollup Summary into the related Opportunity ( Deal__c ) record,   within the custom currency (16,2) field Engagement_Total_Fees__c .  For each Deal__c record there can be one or  many Matter__c  records.
 
I created a Trigger below but it is not working. I believe the trigger does not have coding that will place the currency values in the Total_Fees__c field in Matter__c records to be summarize in the Engagement_Total_Fees__c in the Deal__c record.
 
I am not an expert in triggers and I could appreciate the help.

trigger UpdateEngagementTotalFees on Matter__c (After insert,After update,After delete){
    Set<String>dealIds= new Set<String>();
    if(Trigger.isDelete){
        for(Matter__c mat : Trigger.old){
            dealIds.add(mat.Deal__c);
        }
    }else if(Trigger.isUpdate){
       for(Matter__c mat : Trigger.New){
            if(mat.Deal__c != trigger.oldMap.get(mat.id).Deal__c || mat.Total_Fees__c !=trigger.oldMap.get(mat.id).Total_Fees__c){
                if(mat.Deal__c!=null)
                    dealIds.add(mat.Deal__c);
                if(trigger.oldMap.get(mat.id).Deal__c!=null)
                  dealIds.add(trigger.oldMap.get(mat.id).Deal__c);  
            }
       } 
    }else{
        for(Matter__c mat : Trigger.New){
            if(mat.Deal__c != null){
                dealIds.add(mat.Deal__c);
            }
        }
    }
    if(dealIds.size()>0){
        TriggerUtility.rollupBookValues(dealIds,'Matter__c');
    }
    }