Animating a section of a movie only...how?

Hi there,

Still getting my feet wet in Flash, but enjoying it. I have a project where I have a graphic with 3 separate areas. When you mouse over area A, the client wants a piece of animation to happen based on the static image there.

So example, there’s a tall rectangle on the left side that says “sources” on it. When you mouse over it, it should break up into 9 boxes (that stacked make up this rectangle or pillar) and animate in some fashion with data going to the center part of the movie itself.

When you mouse out, it should return to how it was in the beginning. (with some kind of exit animation)

What is the best strategy for this type of thing? Would I load a movie clip into that part of the flash file (if I can even do that?) on mouse over? Or would that section itself be a movie clip that only plays on mouseover? Or is there another way altogether?

As I said, there are 3 sections of this graphic and they all do similar things. Any help is appreciated! Thanks!

Tom