TargetControlID="MessageTextBox" PopupControlID="Panel2" CommitProperty="value" Position="Bottom" CommitScript="e.value += ' - do not forget!';" /> The RadioButtonList1_SelectedIndexChanged method commits the selected value from the radio button lists to the underlying TextBox control. Other than that, the only other piece worth noting here is the addition of the PopupControl extender with the MessageTextBox control set as its TargetControlID. The CommitScript property just displays additional text along with the selected value from the RadioButtonList control. And that??™s all! It??™s that easy to use the PopupControl extender and associate extra content with a TextBox or other HTML controls. The main common denominator in the supported controls is that they must all have support for a Click event. Rating Control From various product reviews to feedback forms, songs, and other media online, some variation of a Rating control is becoming common on web sites these days.