ActionScript 3.0 :: Comunication Between Two SWF Imported?

have a film with two empty MCs, "mc1" and "mc2", each one load a external swf, so far so good. The film loaded in MC1 must control an especific MC ("mc3") from the film loaded in MC2, and here is the problem. Dont work. I can�t comunicate me with mc3. Here is the code that I use:

link1_mc.addEventListener(MouseEvent.CLICK,link1cl ickPlay);
function link1clickPlay(event:MouseEvent):void {
MovieClip(parent.parent.parent).mc2.mc3.alpha=0.5;
}