How to make a GUI Box drop down menu?

Hey guys,

I am wanting to make it so that when the user hovers over a GUI Button, it makes a sort of menu where more GUI Boxes drop down from the side of that, but when the user takes their mouse off of the first GUI Box, then the drop-down list dissapears (sort of like a CSS navigation bar in HTML).



There is an example on the wiki that may do the trick: