I've been trying to do the same thing - right now I can't even get a button to work, though I can draw one to the screen. It's just not clickable yet. The template code for drawing the interface has a lot of assembly in it, too, so I can't make head nor tail of how you're supposed to do it.
I'm sure if it was hacked at for a while we could figure out how to seperate out all the mouse handling and interface handling code so we could make our own, but there just isn't enough documentation on it to make it happen yet. I'll continue trying to figure it out.