1.5.1.3 - Productfeed for Prisjakt including freight

Hi,
I have downloaded extension "Productfeed för Prisjakt" but need to add freight charge by weight to the file. A majority of other companies present at Prisjakt and other similar sites offering the same products has it. I will only confuse customers if I don't show it like this. When creating the file I need it to take the product weight, get the freight value for the weight. I have only one freight option and due to this only one freight table.
Thanks...