I added this button to my UI mod but unfortunately it doesn't work.

It is supposed to pop up the clock when you hover over an area. Any ideas?
Code:
<Button BackgroundOpacity="0.000" Location="41,0" Name="ClockPopup" OnHoverIn="show_window=(MainHUD.Clock) show_window=(MainHUD.Clock)" OnHoverOut="close_window=(MainHUD.Clock) close_window=(MainHUD.Clock)" Opacity="0.000" PackLocation="left, top" PackLocationProp="0041/0001,0000/0001" ScrollExtent="60,18" Size="60,18"></Button>