I am simply trying to hide a datatip on a chart if the hit data item (yfield item) is == 101 for two differnt series an areaseries and a line series. The following funciton works in IE but throws an error in firefox. I am new to flex and was wondering if there is a better way to approch this.. the code in // is causing the error. public function datatip_M_chart(e:HitData):String { //if (e.item.STUB == 101) {e.chartItem.itemRenderer.alpha = 0}// if (e.chartItem is AreaSeriesItem){ return'<b>'+COMBO.selectedLabel+'</b>'+ '<br/><i>Age: </i>' + e.item.STUB + '<br/><i>Percentage:</i> ' + e.item.M_PROP+'%'; }else{ return'<b>'+COMBO2.selectedLabel+'</b>'+ '<br/><i>Age: </i>' + e.item.STUB + '<br/><i>Percentage:</i> ' + e.item.M_PROP+'%'; }