Menggunakan getBounds()

programnya:
this.createEmptyMovieClip("square_mc", 1);
square_mc._x = 10;
square_mc._y = 10;
square_mc.beginFill(0xFF0000);
square_mc.moveTo(0, 0);
square_mc.lineTo(100, 0);
square_mc.lineTo(100, 100);
square_mc.lineTo(0, 100);
square_mc.lineTo(0, 0);
square_mc.endFill();

var bounds_obj:Object = square_mc.getBounds(this);
   for (var i in bounds_obj) {
   trace(i+" --> "+bounds_obj[i]);
}

hasilnya:
yMax --> 110
yMin --> 10
xMax --> 110
xMin --> 10

sumber:
http://help.adobe.com/en_US/as2/reference/flashlite/WS5b3ccc516d4fbf351e63e3d118ccf9c47f-7cef.html