Mouse Follow with Easing

hello,

Right I followed this tutorial mouse follow and its wot am looking for but the thing I want to do is that I only want the dot to move up & down (which i done) but only to a certain amount?

e.g.

if i got a box, i only want the dot to move up & down in side the box area and not to go out side that area.

Can ne one help me with this?

I attached the fla. to show where abouts I am at the mo.