Help With Menu

I am building my first site in flash and I’m having big trouble (as expected)

I have a menu. Upon clicking on a selection in this menu, a sub-menu rolls out (using a mask).

What I want to acheive is to have the submenu roll back away (again, with a mask) and the new sub-menu (if applicable) to roll out.

You can see where I’m at so far by looking here…
and the source is

Do I need to split up my movie into several different movies to acheive this?

Any help is appreciated.