How to make new texture appear

[LordRevan999]

I have been thinking on this and can't find any answer so can anyone tell me that if I want to use two textures of a wall on a module's wall while keeping both the files in the override folder at same time with different name.And I mean like take example when we visit telos for first time.It has one texture and on our second visit or after any condition the second texture is used in the module.

Is there any script to do that or if not how can I do it?