Google Maps - retrieve Postal codes and cities from Radius

We are an Adwords management company, and we are making a lot of small local campaigns. For this we would like an easy way to retrieve a list of postalcodes and city names from within a radius of a city. This should work in Denmark So an example would be, to retrieve a list of cities and postalcodes from a radius of 10km from copenhagen center, this would give us a list of all those small cities. I am not sure that Google Maps has the postcodes in Denmark, so maybe we would have to provide a list here, that could be paired with the cities found inside the radius. We need this list for keyword generation.