Awwwww dang it's almost the thing I need! : D
I should say dragging with obstacles not with boundaries, so generally you could drag the black box freely but it coudn't go through green boxes! Sorry I understood it only after you put out the .capx.
But this .capx is very useful too, say, it's a good go in some GUI stuff or special gameplay schemes!
Would be cool to see if it possible to make black box drag like that!