MouseEvent target? MouseEvent relatedObject?

I have the following:

rwBtn.addEventListener(MouseEvent.MOUSE_OVER, audioOver);

function audioOver(e:MouseEvent):void

{

     var thisClip:MovieClip = e.relatedObject;

     thisClip.alpha = 0;

}

I would like to change the alpha of the clip that is being rolled over. I don't know how to target the clip that is being rolled over. How do I do that?

Thank you very much!!!