This should be simple enough but for some reason it's not.

I've created a movieClip using illustrator, which is a radial gradient in a rectangle. Original size is 1024 x 125. However I want the width to be whatever size the NativeWindow is. Not the stage but the nativeWindow. No matter what I try the width always comes out to 1024 (unless I specifically give it a size, like headerBg.width = 300. I'd like it to constantly stay the same size as the nativeWindow whenever that window is resized as well, but right now I can't even get the initial instance to display correctly. Any hints?