Floating Datagrid Graphic Problem

[JamesFaron]

I have a floating datagrid in the QueryBuilderWidget from Sample Viewer1.3. This widget was written with a datagrid in the viewstack, and I can created a list event that highlights the graphic on rollover. However, on the Floating Datagrid, I cannot get this to work: I get Error #1009: Cannot access a property or method of a null object reference. The code that generated the error is 'vQW.onItemRollover(event) from this code block:

private function onItemRollOver(event:ListEvent):void
            {  
             highlightedGraphic = findGraphicByAttribute(event.itemRenderer.data)
             var vQW:QueryBuilderWidget = _bWidget as QueryBuilderWidget;
    vQW.onItemRollOver(event);
             highlightedGraphic = findGraphicByAttribute(event.itemRenderer.data)
            }

Any advice will be greatly appreciated.

Thanks,
Jim Faron