Expandable Flash Nav

I am trying to create a nav system that expands to show sub-sections when the user rolls over main section buttons. Let me describe exactly (as best I can) how this would work:
A vertical list of 5 menu buttons is stacked and distributed at equal distances. The user clicks a button (lets say Button 2) and Buttons 3, 4, 5 slide down to reveal the sub-nav below Button 2. When the user clicks or rolls back to any of the original 5 buttons, that subnav closes up.

Does anyone know of a good tutorial for this type of nav or have anything I might be able to dissect and work from? I will try including an example here to clarify what I’m looking to achieve.

Thanks for taking the time to help.