sweeping nport file name with ADEXL

Hi, I saw a thread on that before but the answers were not very clear. I want to sweep the filename of a nport cell. lets say the filename is called sp1.s2p. now i have 100 different files sp1.s2p sp2.s2p ... sp100.s2p. I want to sweep them all using a global variable. The first thing i did is define the file name as a variable in the "Additional parameter list" (file=filename) then i added a global variable called filename = "path/sp1.s2p" this works well. the problem is how i create a second var that will concatenate inside the filename? Is there a better way to do that? Thanks