      *  to see if the item is visible and invalidates the grid if it is. Otherwise, 
      *  do nothing.
      */
-    private function dataProviderCollectionUpdate(event:CollectionEvent):Boolean
+    private function dataProviderCollectionUpdate(event:CollectionEvent):void
     {
         var data:Object;
         const itemsLength:int = event.items.length;

                }
            }
        }
        return true;
    }
    
    /**

     *  Called in response to one or more items having been removed from the 
     *  grid's dataProvider.  
     */
    private function dataProviderCollectionRemove(event:CollectionEvent):void
    {
        const eventItemsLength:uint = event.items.length;
        const firstRemoveIndex:int = event.location;
