Product Filters

Hi

I'm having some difficulty in getting the filters to work as required.

I want to filter against exclusions. So I created a Feature 'Free from' (multiple select box) and added a few variants (Polyester, Fibre)

Then I created a filter on the 'Free From' feature.

Finally I created two products:

Product 1, set feature to Polyester

Product 2, set feature to Fibre

So on the customer screen Polyester and Fibre filters are visible. When the Polyester alone is selected, Product 1 is listed and when Fibre alone is selected Product 2 is listed which is as expected. However if both Polyester and Fibre are selected both products are listed but nothing should be listed as it should be inverted.

How can I achieve this?

Thanks

It is required to examine the fn_get_products function in the (app/functions/fn.catalog.php file) and check how the filters are processed