Create mask, and zoom on image under mask

Hello Forum Members,

I have a question. I think the coding (if possible) would be fairly complex.
Here is what I would like to do.

I would like to have a mask shape that I could drag over an image. The shape will be a circle, sorta like a magnifing glass - transparent (alpha = 0, or alpha < 100).

I would like to be able to drag this shape over the image (this is fairly easy, as I have some code I copied from a kind actionscript programmer, for drag and pan, etc).

Once I stop the drag, I would like to be able to zoom in or out over the area that the "magnifing glass" covers, keeping the base image outside the mask shape visible, and without zooming it.

I am trying to get my company to buy Zoomify - which would probably do something close enough to what i want to do. The company is slow to respond. hence my desire to see if I could create the zoom effect in actionscript, etc.

Any ideas on how to do something like this???

Thanks,
eholz1