The below code shows how to use the class

import druva.NumberUtil;

trace('500 ', NumberUtil.formatterC3(987654321));
// 987,654,321
trace('489 ',NumberUtil.formatterC3(123456789));
// 123,456,789
trace('5 > ',NumberUtil.formatterC3(111222333));
// 111,222,333
trace('1 > ',NumberUtil.formatterC3(556677));
// 556, 677

This is the actual class for validation

package druva{
	import flash.display.Sprite;

	public class NumberUtil extends Sprite {
		public function NumberUtil() {
		}

		public static function formatterC3(number:Number):String {
			//C3 - comma for 3 digits
			var numS:String=String(number);
			if (numS.length>3) {
				var n:Number=numS.length%3;
				var output:String=numS.substr(0,n);
				for (var i:Number = n; i<numS.length; i += 3) {
					output += ((n == 0 && i == 0) ? "" : ",")+numS.substr(i, 3);
				}
				return output;
			}
			return numS;
		}

	}
}