Ultamate noob problem with _x,_y

im sure there is a tuturial on this somewhere but i cant find it. i have a movieclip in a movieclip, and want to find its _x _y on the stage, not just to its _parent, i usualy just use"this._x + _parent._x. But when i rotate the parent it doesnt work, how can i get the _x,_y of an object in an object thats rotating?