>i use mousemove to check if user moves mousepointer to a button, what if i want to check if user's mousepointer leaves the button? what's the counterpart of mousemove then?

Mousemove is an old event, which wasn't too useful for the obvious reason: it didn't have a counterpart, so people sometimes used timers to check if mouse was still over the object.

The better pair (introduced in, I think, v7) is .MouseEnter/.MouseLeave.