Magnification to static location

I have a problem with implementing a magnification application; I just can’t think of how to get it done.

OK. There is a picture on the screen. Where ever you move the mouse a little empty box follows(easy). Below the picture there is an image that displays what is inside the empty box, but it is magnified.

I am thinking that I can have a larger image of the picture out of view and move a large box over that picture that mimics the smaller picture. Then I can “copy and paste” whatever is inside the large box to the magnification stage under the little picture.

Do you guys follow?

Any help would be cool.

Thanks