hello
i have two object sub and account when i add data on sub  like (product name is a filed in sub) it automatically added to account in field product name  but when i added data on same account it replace the priveus one so how can i add multiple data in it
like first product name is gold and when i add another product name like silver then it display like  gold, siver,... etc
 here is my below trigger 
thanks
devendra


trigger copypro  on Subsc__c  (after insert,after update) 
{
    //Id recordTypeId = [Select Id From RecordType Where DeveloperName = 'User Group Membership'].Id;
    Id recordTypeId = Schema.SObjectType.Subsc__c.getRecordTypeInfosByName().get('User Group Membership').getRecordTypeId();

    List<Subsc__c> subscList = new List<Subsc__c>();

    for (Subsc__c s : Trigger.new){
        if(s.RecordTypeId == recordTypeId)
            subscList.add(s);
    }

    Map<ID, Account> Acc = new Map<ID, Account>(); //Making it a map instead of list for easier lookup
    List<Id> listIds = new List<Id>();        
    set<ID>cObjectID = new set<ID>();   //Making a set of Product ID's
    Map<ID, Account> updateMap = new Map<ID, Account>();
  
    for (Subsc__c s : subscList)
    {
        listIds.add(s.Company_Name__c);
      
        if(s.Product__c     != null)
        {
            cObjectID.add(s.Product__c    );//takes the Lookup Record & Add that ID's in cObjectID set
        }
    }
    if(!cObjectID.isEmpty()){
        
        Map<ID,Product2> cObjectMap = new Map<ID,Product2>([select Id,Name from Product2 where Id IN: cObjectID]);
        Acc = new Map<Id, Account>([SELECT id, Product_Name__c,(SELECT ID,Product__c FROM Subscs__r) FROM Account WHERE ID IN :listIds]);
        
        for(Subsc__c s : subscList)
        {            
            if(cObjectMap.get(s.Product__c    ).Name != Null)
            {
                // fill the country name on Opportunity with Country Name on Country_Object__c
                String pro= cObjectMap.get(s.Product__c    ).Name;
                Account myacc = acc.get(s.Company_Name__c);
                if(myacc != null){ //always check for nulls to avoid null pointer exceptions
                    myacc.Product_Name__c =pro;
                    updateMap.put(myacc.Id,myacc);
                }
            }
        }
        update updateMap.values();
    }
   
}