Close swf button

programming flash
1

Hi. I have a button that loads an external swf.
this is the code

map_btn.addEventListener(MouseEvent.CLICK, clickFunction);

function clickFunction(evt:MouseEvent):void {
tint_mc.gotoAndPlay("on");

var request:URLRequest = new URLRequest("SWFS/map.swf"); 
var loader:Loader = new Loader() 
loader.load(request); 
addChild(loader);
}

Now i want that same button to unload that swf-file.
How?

I tried removeChild, but then this error appears:

ArgumentError: Error #2025: The supplied DisplayObject must be a child of the caller.
at flash.display:isplayObjectContainer/removeChild()
at menu_fla::MainTimeline/clickFunction2()