Positioning movieclip

1

trying to position a movieclip. using the following code no problem:

onClipEvent (load) {
	_x = 420;
	_y = -40;
	speed = 6;
}
onClipEvent (enterFrame) {
	endX = (Stage.width)/2;
	endY = (Stage.height)-50;
	_x += Math.round((endX-_x)/speed);
	_y += Math.round((endY-_y)/speed);
}

but how do i get the movieclip to position for example at say two thirds the screen width or always stay at a position which at a third of the screen width.

endX = (Stage.width)/2; i’ved tried using ‘3’ and .75 as a fraction for three quarters… what is the proper way to postion something as a percentage or fraction of the screen?

thanks