I have a problem in a product collection that I need to filter. I have a multiselect list with countries. When a selection is made the products need to be hidden from these countries.
$collection->addAttributeToFilter('available_not_for_countries', array(array('nin' => $billingCountry),array('null' => true)));
I know I need the opposite of finset like NOT FIND_IN_SET but I have no idea how to create the new Zend_Db_Expr for this in this filter.