Removing Children previously created with AS3

programming flash
1

Here’s the AS code:
//-------------------------
//----DESIGN BUTTON----\
//-------------------------

design_btn.addEventListener(MouseEvent.MOUSE_OUT, dOut);
design_btn.addEventListener(MouseEvent.MOUSE_OVER, dOver);

function dOut(event:MouseEvent):void{
design_btn.alpha = 1;
}

function dOver(event:MouseEvent):void{
design_btn.alpha = 0.8;
}

// Put the panel in its starting (closed) position.
designbox_mc.x =125.2;
designbox_mc.y = 270;

// Add listener to the button so a mouse click will slide the panel
design_btn.addEventListener(MouseEvent.CLICK, growdesignBox);
designclose_mc.addEventListener(MouseEvent.CLICK, shrinkdesignBox);
designclose_mc.buttonMode =true;
design_btn.addEventListener(MouseEvent.CLICK, viral);

    //-----------------------
    //----DESIGN THUMBS-------
    //-----------------------
//this function is loading the thumb holder dynamically

function viral(event:MouseEvent):void {

    var designbox_mc:Loader = new Loader();
    var thumbs:String = "design.swf";
        
    var imageRequest = new URLRequest(thumbs);
        
    designbox_mc.contentLoaderInfo.addEventListener(Event.COMPLETE, onComplete);
    
    designbox_mc.load(imageRequest);
        
    function onComplete(evt:Event) 
    {
    
    addChild(designbox_mc.content);
    designbox_mc.content.x = 0
    designbox_mc.content.y = 300
    }

}

function growdesignBox(event:MouseEvent):void{
var designbox_mcYTween:Tween = new Tween(designbox_mc, “height”, Elastic.easeOut, 0, 215, 3, true);
}

function shrinkdesignBox(event:MouseEvent):void{
var designbox_mcYTween:Tween = new Tween(designbox_mc, “height”, Strong.easeOut, 215, 0, 2.5, true);
}

…the problem is trying to remove the child.