grid_controller.rb

    if @related_products
      # delete related not in the current marketplace
      @related_products.delete_if do |p|
        p.nil? || !p.marketplace_ids.include?(@marketplace.id) 
      end
      # delete related not in order 
      @related_products.delete_if do |p|
        p.marketplaces_products.find_by_product_id(p, :conditions => [ "product_order < 0" ]) ? true : false 
      end
    end