Not tried this, but used some of the databases for other things.

http://www.ip2location.com/ip-countr...e-zipcode.aspx

above will get you the users zip code along with latitude-longitude

below is for asp users to calculate the distance between latitude and the
longtitude. they have this avail for other code formates too.


ASP
http://www.geodatasource.com/samples/distance.asp.txt

calculations for other programming languages

http://www.geodatasource.com/developers.html

k