Natools

            Previous : Callback_Refs.Reference;
         begin
            Map.Insert (Actual_Time, Callback, Position, Inserted);

            if not Inserted then
               Previous := Entry_Maps.Element (Position);

               if Previous.Update.Data.all in Event_List then
                  Append
                    (Event_List (Previous.Update.Data.all),
                     Callback);
               if Previous.Query.Data.all in Event_List then
                  if Callback.Query.Data.all in Event_List then
                     for I of Event_List (Callback.Query.Data.all).List loop
                        Append (Event_List (Previous.Update.Data.all), I);
                     end loop;
                  else
                     Append
                       (Event_List (Previous.Update.Data.all),
                        Callback);
                  end if;
               elsif Callback.Query.Data.all in Event_List then
                  Append (Event_List (Callback.Update.Data.all), Previous);
                  Map.Replace_Element (Position, Callback);
               else
                  Map.Replace_Element
                    (Position,
                     Create_Event_List (Previous, Callback));
               end if;
            end if;
         end;