How Do I Make a GUI?

[rockslide26]

I saw a really cool RPG in a server, and It had this really cool trading GUI where you could trade items/exp/gold for another player's items/exp/gold. How would I make a GUI like this?

[Ad Bot]

[Smeeble]

I could probably make one if I knew how, but then you'd have to script it. lol

[_Rave_]

Unless you can script just forget this idea.  Sorry.

[jes00]

I saw a really cool RPG in a server, and It had this really cool trading GUI where you could trade items/exp/gold for another player's items/exp/gold. How would I make a GUI like this?

What server was it?