Help with movieclip/button containing sub movieclip/buttons

Hi Im trying to create a certain type of button.
An example of this type of button can be seen on the navigation on the following website:

The rollover button contains a movieclip and inside this movieclip ther are several other rollover buttons which lead to other sub-movie clips.
Does anybody have a similar working example so as I could look at the actionscript I cant seem to find anything online?
All help would be much appreciated…