thanks, there was one typo but fixed it and yes it works.

However, when I deploy to production I get too many SOQL queries, this is the full code which I'm pretty sure is now fine.

   {     
       Map<Id,Map<Id,CampaignMember>> map_ContactID_Members = new Map<Id,Map<Id,CampaignMember>>();

    for ( Course_Application__c application : Trigger.new )
    {
        map_ContactID_Members.put( application.Course_Applicant_del__c, new Map<Id,CampaignMember>() );
    }

    for ( CampaignMember member :
        [   SELECT  Id, ContactId, CampaignId, Status
            FROM    CampaignMember
            WHERE   ContactId IN :map_ContactID_Members.keySet()
        ]
        )
    {
        map_ContactID_Members.get( member.ContactId ).put( member.CampaignId, member );
    }

    List<CampaignMember> list_CampaignMembersToUpsert = new List<CampaignMember>();

    for ( Course_Application__c application : Trigger.new )
    {
        Map<Id,CampaignMember> map_CampaignMembers = map_ContactID_Members.get( application.Course_Applicant_del__c );

        if ( map_CampaignMembers.containsKey( application.PullCampaignID__c ) )
        {
            CampaignMember member = map_CampaignMembers.get( application.PullCampaignID__c );

            member.Status = application.Status__c;

            list_CampaignMembersToUpsert.add( member );
        }
        else
        {
            list_CampaignMembersToUpsert.add
            (   new CampaignMember
                (   ContactId   = application.Course_Applicant_del__c,
                    CampaignId  = application.PullCampaignID__c,
                    Status      = application.Status__c
                )
            );
        }
    }

    upsert list_CampaignMembersToUpsert;
    	   
    	   
    	  // for(Course_Application__c d:Trigger.new)      	
       // {CalcNumberOfCourseApps.CalcApps(d.Course_del__c);
       // }
    	
    	
	Map<id, Integer> coursesToassigntsMap = new Map<id, Integer>();
	  set<Id> courseIds = new Set<Id>();
	   for(Course_Application__c a: trigger.new){
		   courseIds.add(a.course_del__c);	   
   		}
   	    list<course__c> CList = [Select id,Confirmed_applications__c from Course__C where id in :CourseIds];
	   
	   
	  for (AggregateResult agr :[select count(id) idCount,course_del__c from Course_Application__c where course_del__r.Id in :CourseIds and status__c='Ordered'group by course_del__c])
	   						     
		{
          coursesToassigntsMap.put((ID)agr.get('course_del__c'), integer.valueof(agr.get('idCount')));
         
		}
	   
	  List<Course__C> UpdateList = new List<Course__C>();
		for(course__c ids: CList)
		{
		
		ids.Confirmed_applications__c = coursesToassigntsMap.get(ids.id);
		UpdateList.add(ids);	
	}	

	if(UpdateList.size()>0)
	Update UpdateList;	

 but I also have another triggger that fires on the same object, could this cause the problem?  If so here's the code.

  //Limit the size of list by using Sets which do not contain duplicate elements
  set<Id> MyOrderIds = new set<Id>();

  //When adding new payments or updating existing payments
  if(trigger.isInsert || trigger.isUpdate){
    for(Course_application__c p : trigger.new){
      MyOrderIds.add(p.MyOrder__c);
    }
  }

  //When deleting payments
  if(trigger.isDelete){
    for(Course_application__c p : trigger.old){
      MyOrderIds.add(p.MyOrder__c);
    }
  }

  //Map will contain one Opportunity Id to one sum value
  map<Id,Double> MyOrderMap = new map <Id,Double>();

  //Produce a sum of Payments__c and add them to the map
  //use group by to have a single Opportunity Id with a single sum value
  for(AggregateResult q : [select MyOrder__c,sum(cost__c)
    from Course_application__c where myOrder__c IN :myOrderIds AND Status__c<>'Cancelled' AND Status__c<>'Error' and Status__c<>'Transferred out to' group by myOrder__c])
    
    {
      myOrderMap.put((Id)q.get('myOrder__c'),(Double)q.get('expr0'));
  }
  
  List<myOrder__c> myOrdersToUpdate = new List<myOrder__c>();

  //Run the for loop on Opportunity using the non-duplicate set of Opportunities Ids
  //Get the sum value from the map and create a list of Opportunities to update
  for(myOrder__c o : [Select Id, Pre_Discount_Total__c, Discount_Amount__c, to_be_charged_total__c,Total_Collected__c, payment_status__c from myOrder__c where Id IN :MyOrderIds]){
    Double PaymentSum = myOrderMap.get(o.Id);
    if(PaymentSum==NULL){PaymentSum=0;}
    o.Pre_Discount_Total__c = PaymentSum;
    if(o.Total_Collected__c-PaymentSum==0){o.payment_status__c = 'Settled';}
    if(o.Total_Collected__c-PaymentSum - o.Discount_Amount__c<0){o.payment_status__c = 'Balance Outstanding';}
    if(o.Total_Collected__c-PaymentSum>0){o.payment_status__c = 'In Credit';} 
    myOrdersToUpdate.add(o);
  }
 
  update myOrdersToUpdate;