if i purchase this game through GOG will I be able to use some sort of code to unlock it in steam?

No.

You can, however, add it as a "non-Steam game", which will put it on your Steam library list even though it's not a Steam game. I'm pretty sure that can be done with any game.

Why do you want it on Steam?

Maybe he wants all of his games listed on steam, so they fare all gathered in one easy to use list. I know I sometimes forget about some of the non steam games I have installed, though I've never bothered doing that.

ive added em once and after reinstalling steam ou can do it all again :)