QuickBase API Call - Need Formula URL to return data to a field

I have a QuickBase app which I want to pull mileage distance using this website here: [login to view URL] I need my formula URL field to be coded so it will take the returned information and put it into a mileage field when the record is opened. I have the URL setup to return XML showing the result, but need to to automatically update the resulting mileage to my Mileage field. Here's the URL formula I have: "[login to view URL]"&[Tank - Location - Address: Postal Code]&"/mile" QuickBase knowledge is required.