Convert Zip code to Google Metro Code?

I know that Google publishes its "metro areas" for adwords. Is the开发者_C百科re a converter from ZIP code to metro area code available? The metro list I'm referring to is at: http://code.google.com/apis/adwords/docs/developer/adwords_api_us_metros.html

Google's metro names appear to be restricted to USPS post office names, so you can do the conversion with 2 tables:

• The USPS city-state file, which lists all ZIP codes and the corresponding place names and post office names attached to the ZIP. Beware, this file is updated monthly, and the "free" versions floating around and copied from purchased USPS files are often out of date.

• Google's metro list, normalized so entries like "Huntsville-Decatur (Florence) AL 691" become "Huntsville AL: 691/Decatur AL: 691/Florence AL: 691".

Find the ZIP in the city-state file, fetch the corresponding post office name, find the post office name in the normalized metro list, fetch the corresponding metro code.

There's been a couple of similar questions directed towards the adwords API team. In both cases, there answers have been "no, there's no easy way to do that." Jeff Posnick of the adwords team does offer an interesting idea though:

I don't know if there's a way to get clever with one of the geocoding APIs and determine overlaps between cities/zips and those metro area

http://groups.google.com/group/adwords-api/browse_thread/thread/e514fa91403397ab https://groups.google.com/group/adwords-api/browse_thread/thread/1af97ae9938d76ee