Zackary - don't have alot of time to look at this, but basically in addpost.php you're looking for this:
if(($config['files']) && ($Reged == "y")) {
$attachfile = "<br /><br />{$ubbt_lang['YES_FILE2']}";
$fileinput ="<input type="file" name="userfile" accept="*" class="formboxes" size="60" />";
}
Above it add -
if ($Board == "keyword") {
and below it add:
}
That'll remove the box if they aren't in the board(s) that you want.

Hope that gets you going in the right direction.
