Script for UPS shipping codes

I use UPS to ship products and they have a bizzare shipping cost structure based on zones that are determined from your zip code. For example, if your zip code is 87114, you look up that zip code on the table, it tells you that you are in “zone 4” and thus your shipping is $xx.xx

Has anyone ever seen a script that would determine the shipping zones based on zip code? I currently have the user look up their code for themselves, but it would be nice if they could simply pop up a small input box, type in their zip code, and be told what their shipping zone is. Any example of how to handle this would be greatly appreciated.

Thanks
Fedman