A Trade systeme is missing for my rpg(multiplayer)

A Trade systeme is missing for my rpg(multiplayer)

Evry body i am making an rpg and i need a trade systeme could any body suggest me something or make a trade systeme for me that would be usefull cuz my rpg is much like diablo 2 you know get items and trade tem but i dont have a trade systeme!(I will give Credits)

This better haven't come out of the idea of battleships or else. You would need a hell of a lot of If-Then-Elses plus conditions