"Sign Up For Battle" Modification

[hyperviperx99]

I have an online rap battle and poetry battle forum, and usually if a member wants to battle, they comment on the "sign up thread". Some new members are confused about how to sign up at first, so I want to find out if there's a modification where I can get a "Sign Up For Battle" button, and it will be put in the list of players who signed up for a battle.

Please let me know.