Resize one side of sprite and interrupt tween

Hey,

In my Actionscript 3 program I would like to resize a sprite, but only one one side. The bottom position, left side and right side shouldn't change, only the top (stretching). However, I have no idea how to accomplish this.

The second problem that has to do with resizing the sprite, is that I would like to interrupt the resizing with a keyboard event. When the sprite is resizing, a user should be able to press a button. This event should be excecuted before the resizing (tween?) has finished. Is this possible?

Hopefully someone can help me.

Thanks in advance