Help needed with AS movement

Hi all, over the past few days I’ve been trying to get to grips with movement in AS and there seems to be a veritable feast of information out there regarding it. I’ve had a lot of help from various people on these boards and I want to say ‘thanks’ to all those who’ve helped me out.

BUT - If I could indulge upon your good natures again…

I’ve put together a small piece utilising various bits of code that I’ve gained from helpful posts in which buttons move an instance around the stage on the X&Y axis but I don’t know how to constrain the instance to the stage. Could anyone help me?
I’ve attached an FLA.