WoW | Round robin 20boxing

So I stuck at the setup of Round robin. I got 20 Characters and I only want character 15-20 to do a round robin on key T and F.

[lax]

Start by creating an Action Target Group with the Characters in it that you want in the round-robin. Then you can use the Mapped Key Wizard to set up a "Round-Robin Key Broadcast" in your Combat Key Map, using that ATG as the Target for the round-robin.