Movieclip button within movieclip button

hi Im trying to make a button - once the button is rolled over it plays a movie in which the button grows in size. Once the cursor rolls off the button the movie clip frames play in reverse order and the button shrinks in size.
No problem - I can do this much…

However if I want to include a sub-button inside my first movieclip/button…
The problem is that once I rollover the first button to make the sub-button appear…once I rolloutside my first button area to click on the sub button the 1st movieclip button returns to frame one, the sub movie disappear and I am unable to select the sub-button.

Here is an example of what I am trying to achieve http://www.minipixel.com/isomenu.html

I can achieve this using ‘on mouse release’ but I want to have the same interaction using the mouse over and mouse out techniques.

I hope this makes sense.