How to make (Post Process) Effects only on a texture?

Hi,

i have created a minimap. The minimap texture gets its data from a material.
Within the material there is a texture that gets its data from a scene capture 2D.

How can i change the look of just that texture. I want an outline and paper effect.

I know there are post process materials out there, but i just want to change the look of the minimap, not the world.

Thanks in advance