$prereserve=array();
        $prereserve[] =& HTML_QuickForm::createElement('text','prereserve_time',"");
        $prereserve[] =& HTML_QuickForm::createElement('text','prereserve_room',"");
        $this->addGroup($prereserve, 'prereserve', NULL,NULL,FALSE);
	$ret=$this->addRule(array('prereserve_time','prereserve_room'),
	                    get_vocab("errfield_selected_date_invalid"),'callback',"make_prereservation");
	if (PEAR::isError($ret)) { 
	    echo $ret->getMessage();
	    echo $ret->getUserInfo();
	}