GeoLocation handling

[Dawg]

Hello Everybody,

I'm working on a application similar to a classified ad where the user gets a listing of items within there town and if nothing  is available within the users town I like the ability to extended to the next town by picking distance in km.

I'm able to get the current user location via Javascript method  GeoLocation.getCurrentPosition() but how do i go about adding for example 10km to the  latitude  and longitude to extend the search.

Any ideas as to how to do this would be greatly appreciated.

Thanks