Can't apply button event to child.swf

Anyone know how to control a child swf button from a parent swf? I need to have all my code ONLY in the parent swf; so, how would I apply an onRelease, for instance?

Here's my code: (what I think should work, but doesn't)
All swfs are in same directory, no typos on names.
childMenu.swf has a button with instance name: "buttonName"

this.createEmptyMovieClip("childSwfMovie", 15);
loadMovie("childMenu.swf", "childSwfMovie");

childSwfMovie.buttonName.onRelease = function() {
trace("you've released the button");
}