Magnifying an Image on a mouse rollOver

I was not able to find a thread on this, but I am sure it has been done. What I would like to do is have an image and roll over that image with say a box that would magnify everything in side the box, and the box gets its movements from my mouse movement.
Does this make sense?

You just need to overlay the normal image with a magnified version of that image, and then use a mask that attached to the mouse position to reveal part of the magnified image.

Try something like this: