Dynamic Magnifying Glass

Hello Everyone,

I already posted about this in the general AfterFX discussion group, and I've told I may have better chance in solving this here.
Sorry if I copy and paste from there:

Let me apologize for my bad english in advance, hopefully I will manage to make this as clear as possible.
I'm trying to create a Dynamic magnifying glass.
I have a big composition (w=5000px lh=1440px) that I will use both as the magnified part (masked of course) and as the part to be magnified.
I've created an object that will be my "lens", made of two circles, one that would be the highlighting part, and one that will contain the magnified version.
I've linked everything to a null object, and by doing this I managed to move the mask around the big composition according to the movement of the little highlighting circle, but what I basically need to do is to dynamically move the composition too so that the highlighted part and the magnifyed part match.
I cannot use the Magnyfing glass effect that is in the tutorial section as it's important that the magnifyed part doesn't loose quality and that the image is as clear as possible.
And I need to separate have the highlighted part and the magnifyed part both visible.

I think I should link the center of my highlighting circle to the position of the big composition somehow, but the position value have to go opposite of the movement I make with the highlighting circle (that is, if I move to the left, the composition need to move to the right, sort of like how the camera works when you move it around and you have 2 layers very distant one from the other)

Help!
How can I do this? Is this possible at all?

Thanks
V.