Try this my Friend ... this was done for me by someone here but I forgot who it was ...
make a new plugin :
Hook Location: newthread_form_start
Code:
if ($foruminfo['forumid'] == 14)
{
$newpost['message'] = "
You can replace this with anything you want
You can add anything anywhere between the " " .....
";
}
Replace the forum ID with the forum in which you which to have this at ...
Hope it helps you my Man !