Tweening/resizing graphics.drawRoundRect

I used AS3 to create a rounded edges box, and when the window resize i wanted to keep the ellipse height and width of the edges. How can I do that?

Creating the box

private function detectStage(e:Event=null):void {


            //drawRoundRect ( x , y , width , height , ellipse width , ellipse height )

This 1 the box doesnt change,createBoxx.boxY,sContent.width,sContent.height,10,10);

This makes the overall size strech

widthTween=new Tween(sBox,"width",Elastic.easeOut,sBox.width,boxWidth,2,true);
heightTween=new Tween(sBox,"height",Elastic.easeOut,sBox.height,boxHeight,2,true);