Multiple specular images?

I am working on floor tiles in Sim 4 Studio and I would like to have 2 different specular images for 2 different swatches within the same package. I found on google one post about how to do it, but explanation is too basic for me to understand it (it's a shot post, not a tutorial how to do it). If someone would please help me with that I would really appreciate it. Please, reply here or msg me privately. :)