Draw a shape with a registration point bottom left?

1

I need to have 2 kinds of masks, one with a registration point in the top left so that when I tween its height it expands downwards, and one with a registration point in the bottom left so that when I tween its height it expands upwards?

how do i do that, with code ofcourse?

i have made something but i dont know if its the right way:
(this expands downwards, but i dont know how to get it to expand upwards)

import gs.TweenLite;

var subMask:Shape = new Shape();
var gr:Graphics = subMask.graphics;

gr.beginFill(0x0000FF, .2);
gr.drawRect(0, 0, 100, 1);
gr.endFill();

addChild(subMask);

TweenLite.to(subMask, 1, { height: 100 });