Apply mask so that it only affects one layer or instance

Been thrashing out an idea for a basic photo editor.

Load photo and make changes to photo through basic functions.

The problem arises when I come to zoom into the picture.

Zoomed 150% problem (scaled up 1.5)

As you can see the left picture overlaps the right picture

Desired result

Would like to pan and move both zoomed in photos at the same time also.

I have tried the mask method but unfortunately this masks out the photo on the right also.

I have tried moving the photos to different layers but this has the same affect except the right overlaps the left this time.

In Flash there was a method to apply a mask and it only affected the layer directly below.

So the question is can a mask be specifically applied to only affect a certain instance or layer?

Or is there another way of achieving this?

Or is this totally outside the bounds of what can be achieved?

Thanks

In the layer properties set force own texture to yes..

Hmm it's just not working.

Tried putting one photo on the layer above and creating it's own mask.

But the issue is still that a mask seems to apply to all the layers below it and not just the immediate layer below it.

I guess you were trying Something like this

Wow thanks, that is beautifully simple.

Your help is much appreciated.

All the best.