Custom per-instance material parameter

Hello,

I am using instancedstatic mesh heavily in my application, because I have a lot of static identical objects to render and I think it’s faster than having
round 2000 staticmesh to render. (consider that I do VR on desktop, so I need 90 fps)

On each instance I would like to apply a texture. This texture is a big atlas and I would like to specify somewhere
that each instance should sample just a portion of this atlas.

How can I do?

Thanks in advance,