[kh99]

If you look in banning.php around line 261, there's this code:

	// check that the number of days is valid
	if ($vbulletin->GPC['period'] != 'PERMANENT' AND !preg_match('#^(D|M|Y)_[1-9][0-9]?$#', $vbulletin->GPC['period']))
	{
		print_stop_message('invalid_ban_period_specified');
	}

you'll have to add h to the (D|M|Y) part to allow it as valid. Also, because it uses the function convert_date_to_timestamp() (in includes/functions_banning.php) to calcualte the lift date from the "period", it looks like you'll have to use lower case h instead of H.

Another issue may be that because the bans are lifted by a scheduled task, you'll also have to make sure that that task runs more often than once a day. ETA: ... turns out it does run once per hour by default.