Adds an event handler for the "buttonDropDown" event notification. This event is sent whenever a button on the ToolBar that has the style DROPDOWNBUTTON is pressed. If the button hasn't been told to automatically display a menu, this event is fired, which lets you display some sort of UI representing the drop-down. Note that duplicate adds are not filtered out.
[Visual Basic] Public Sub AddOnButtonDropDown( _ ByVal handler As ToolBarButtonClickEventHandler _ ) [C#] public void AddOnButtonDropDown( ToolBarButtonClickEventHandler handler ); [C++] public: void AddOnButtonDropDown( ToolBarButtonClickEventHandler* handler ); [JScript] public function AddOnButtonDropDown( handler : ToolBarButtonClickEventHandler );