Set ButtonBar's toolTipField to point to field in data provider ToolTips from myToolTip field
<?xml version="1.0"?> <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"> <mx:ButtonBar toolTipField="myToolTip"> <mx:Object label="OK" myToolTip="OK tip" /> <mx:Object label="Cancel" myToolTip="Cancel tip" /> </mx:ButtonBar> </mx:Application>