something else is I believe that eBay has a rule about adding forms code to a listing...and the utility recommended seems to generate HTML form code...you might want to verify this.

If it is still against the rules then simply have your calculator open a new window will get you around the restriction.

And even if you see other sellers using forms in their listings...don't...if someone, who feels they are hall monitor for the day, sees it and reports it you could have a potential headache on your hands...

As all of the major carriers have an API &/or web services which can be called; you can always develop your own shipping tool/calculator...they are pretty straight forward making the call to and getting data back.

Anyway good luck and DO NOT use any of eBay's code...learn from it but don't scarf it as yours...