Customization sort options price - CS-Cart

I am building a webstore and my products have price zero, and only have price by options. In the list products on storefront the products are displayed (with prices) but they can't be sorted by options price (if i select this sort).... but the price are listed in category page / storefront.... Also the filter slider price don't work, are set to zero.... Needs: - We should modify product filters and product sorting on the Category and Search results pages in the storefront. - It should work for products with Price=0.