There are plenty of information sources on the Internet that provide us with usable data, for example exchange rate, RSS-feeds, package tracking, post code validation etc..
The Scandinavian logistic company Bring (
http://www.bring.no) has a public API to access the postal codes for some countries.
The api instruction could be found here
http://developer.bring.com/api/postalcodeapi.html#xml
In this example I will show one way to receive information, it could be use to validate post code in NAV 2013 and ill think it would work in NAV 2009.
Check out my mibuso blog for full information and download example code.
http://mibuso.com/blogs/rikardh/2013/01/13/get-xml-from-internet-and-use-in-nav2013-nav2009/