[Plugin WP e-commerce]: How to get shipping options without page refresh?

Currently, the shipping methods/prices are only displayed once the user selects their country (then state if in USA/UK) then zip/post code.. However, this is all done on page-refresh and each time the user makes a selection from the dropdown or enteres a post code, etc. the page refreshes which has been a big annoyance for many customers.

How can we go about still using ajax to pull in the shipping options and pricing but without a page refresh? Which file would have to be edited or what needs to be tweaked?

Thank you!!