Change Font Size to Fit TextField AS3

public function Autosize(txt:TextField):void {
var maxTextWidth:int = 200;
var maxTextHeight:int = 200;
txt.width = maxTextWidth;
txt.height = maxTextHeight;
var maxTextHeight:int = 200;
var f:TextFormat = txt.getTextFormat();
//decrease font size until the text fits
while (txt.textWidth > maxTextWidth || txt.textHeight > maxTextHeight) {
f.size = int(f.size) - 1;
txt.setTextFormat(f);
}
}