Как сделать обязательные поля при создании товара? - [VM2&3] Модификации и хаки

<select class="inputbox width100" id="categories" ...

<select class="inputbox width100 required" id="categories" ...

<?php echo $this->lists['manufacturers'];?>

<?php //echo $this->lists['manufacturers'];
$manufacturers = VmModel::getModel('manufacturer')->getManufacturers(false,true);
$mf_attrs = array();
$mf_attrs['class'] = 'width100 required';
$mf_attrs['multiple'] = 'multiple';
echo JHtml::_ ('select.genericlist', $manufacturers, 'virtuemart_manufacturer_id[]', $mf_attrs, 'virtuemart_manufacturer_id', 'mf_name', $this->product->virtuemart_manufacturer_id);
?>