arcgis flex api - Help needed for extended symbol

I am trying to extend Symbol class in ARGIS Flex API. this is my widget named TestWidget http://pastebin.com/04w6RSur and here is the extended symbol class http://pastebin.com/bqhDzdSe named CustomSymbol placed in Test package in flexviewer 2.

I had drawn a circle and a line in CustomSymbols sprite like this:

sprite.graphics.beginFill( 0x0000FF,1 );
sprite.graphics.drawCircle(0,0,100);
sprite.graphics.endFill();  
sprite.graphics.lineStyle(5,0xFF0000,1);
sprite.graphics.lineTo(mapPoint.x+100,mapPoint.y+100);

when I zoom into map it shrinks its size and when I zoom out it grows accordingly. What I want is make it retain its size whether I am zooming in or zooming out.

Thanks