[Xenon]

hmm, it's not a fine way, but should work:

open newreply.php and find:

PHP Code:

// ### CHECK IF ALLOWED TO POST ###
if (!$threadinfo['visible'] OR $threadinfo['isdeleted'])
{
    $idname = $vbphrase['thread'];
    eval(print_standard_error('invalidid'));
} 


and below add:

PHP Code:

// ### CHECK IF THIS IS A SPAM FORUM AND JUST ALLOW XX POSTS PER DAY ###
if ($threadinfo['forumid'] == XX)
{
    $posts = $DB_site->query_first("
        SELECT COUNT(postid) AS spamposts
        FROM " . TABLE_PREFIX . "post AS post
        INNER JOIN " . TABLE_PREFIX . "thread AS thread USING(threadid)
        WHERE post.dateline > " . (TIMENOW - 24 * 3600) . "
            AND thread.forumid = XX
    ");
    if ($posts['spamposts'] > 30)
    {
        eval(print_standard_error('toomuchspam'));
    }
} 


now all you have to to is to create a new errorphrase called toomuchspam