[as2] Collision Detection

Hi.
I´d like to know how can I make a collision detection between two objects with complex shapes.

Each object has a parent movieclip.

Example:

_root.obj1.child
_root.obj2.child

I need to make a collision detection test between each child of those two objects.

As far as I know. I can use the hitTest for bitmap. But isn´t working.
I´m not finding the right way to do it.
I think it needs localToGlobal for x and y for each child clip coordinates and matrix, because obj1.child and obj2 rotates on _root.onEnterFrame.

The function itself would be something like this:

function checkCollision(a:MovieClip, b:MovieClip):Boolean{
var boolean:Boolean = a.hitTest(b)
return boolean
}

And the function call would be something like this:

checkCollision(obj1.child, obj2.child)

Anybody know how?

Please, I can´t use GSkinner´s class.
Ah, and that way of creating empty movie clips surrounding the shape´s edges takes too long for me because I have a lot of objects.

Thanks