Hello, I have a question about a menu's rect.

Hi!
I'm having a problem. I want to know a menu's rect when the menu pops up, now I know the menu's
hMenu, how to do it?
I snapped a picture to show what rect I want to know, have a look at this picture, the red rectangle
is what I'm talking about.

http://prefix.533.net/menu.jpg

Thanks you!