[insanctus]

Make a new profile field they can edit in usercp if they wish to be locked at 420

Make the options Yes No

Make sure you look up the field number

Open includes/function_newpost.php

Find

		$DB_site->query("
			UPDATE " . TABLE_PREFIX . "user SET
				$doposts
				$dotitle
				lastpost = " . TIMENOW . "
			WHERE userid = $bbuserinfo[userid]
		");

Above it add

if ($bbuserinfo[fieldnumber]=='Yes' AND $bbuserinfo[posts] >= 420)
{
$doposts = 420;
}

Replace the above with the correct field number it shows in profile field area exp field4

Hope that helps.