Automatically detect region/continent from country select

[chibineku]

I have been messing about with ways to assign a region to shoppers on my site to determine postal rates. At the moment, during registration there is a SELECT with the different regions, which will be UK and then the other continents. Most websites detect this automatically, though, and I figure there must be pre-made databases or drop downs available with such information stored in the value for each option. I already have a database associating each country with it's ISO, which had to be done from combining two different freeware SELECTs that I found online. I can't seem to find something that suits this purpose though. Short of assigning a region code to each of over 200 countries, how do I do it? How does Amazon decide, when I choose United Kingdom as my country, what my postage will be?

[dsonesuk]

this link looks like it could be helpfulhttp://www.justin-cook.com/wp/2006/11/29/d...eir-ip-address/