Jake's framework covers this to some degree. IGlass and FryGui are both as easy to use as MaxGui (which I wouldn't use for a game interface).
If you want to do it yourself then I would either go for the Collision Layer for GUI suggestion or by the rect collision test and then an ImagesCollide on buttons close enough to count.
If you want to do it yourself then I would either go for the Collision Layer for GUI suggestion or by the rect collision test and then an ImagesCollide on buttons close enough to count.