Instances inside an Attached Movie

How do I manipulate an Instance inside an attachedMovie ?

For example, I create an createEmptyMovieClip and attach a Movie to it. The movie attached to it has an instance called mc_mask and I want to move that instance from outside that movie (from where I created the empty clip).

This dosn’t seem to be an issue with loading external SWF, with attached Movies it seems to be differen.t

Got it already. It seems that attachMovie dosn’t repleace the movie, it actually adds it.