Can a created "createEmptyMovieClip" movieclip have a rollOver state?

… because I can’t get it to work!

var thumbBalcony:MovieClip = this.createEmptyMovieClip("thumbBalcony",this.getNextHighestDepth()+3);
thumbBalcony.loadMovie("flash-balcony-small.png");

thumbBalcony.onRollOver = function():Void {
    thumbNoteOut("thumbBalconyText");
}

Is this supposed to be like this? Orrr am I missing something?