only 1 Public usergroup, have code (think)

[FrozenCreations]

ok, i was taking a wiz, and i had an idea on how 2 get this code to work verry easy!

all i need to know is, where do i put it?

PHP Code:

if (is_member_of($bbuserinfo, 25)) {
echo 'Sorry, you are already part of a usergroup';
}
else {
Code 2 make user a part of a usergroup
} 


would that work? and if not, can you suply what i missed ^^;

im guesing the code is somewhere in the options.php