[mx04] movieclip onRelease remove itself?

I’m loading an external swf with a movieclip button, and at the same time loading a “close” movieclip on the main timeline near it to close the external swf.
All works fine except that I’d like the "close’ movie clip to also remove itself on release. I can’t seem to get it right.
here’s what I have

var thisRoot:MovieClip = this;
         thisRoot.attachMovie("iTWorks_btn","wrk1_btn", 2030690070);
wrk1_btn._x = 169;
wrk1_btn._y = 432;
thisRoot.wrk1_btn.onRelease = function(){
    empty_mc._x = -90;
    empty_mc._y = 100;
    //attach close_btn
    thisRoot.attachMovie("close_btn", "cls_btn", thisRoot.getNextHighestDepth());
    cls_btn._x = 715;
    cls_btn._y = 250;
    thisRoot.cls_btn.onRelease = function(){

this removes the loaded swf, but the cls_btn still stays on the stage.
Anyone know how to do this?