The below code shows how to calculate distance between two points in as2

 private function distanceBetween(var x1:Number, var y1:Number, var x2:Number, var y2:Number):Number {
  var diffX = x2-x1;
  var diffY = y2-y1;
  return Math.sqrt((diffX*diffX)+(diffY*diffY));
 }
trace(distanceBetween(20,20,100,100));