Unloading a movie with a button click in loaded movie

1

I have a movie clip (a) with a button that will load movie clip (b) when clicked. It loads (b) on top of (a) which is exactly what i want.

Now the problem. I have a button in (b) that I want to use to close (or unload) (b).

This is the code in (a) that loads (b):

spinner_mc.production.addEventListener(MouseEvent.DOUBLE_CLICK, doubleClickHandler2);
function doubleClickHandler2(event:MouseEvent):void {
    var myLoader:Loader = new Loader();
    addChild(myLoader);
    var url:URLRequest = new URLRequest("production-04.swf");
    myLoader.load(url); 
}