Possibility to have drop down selection list instead of free text entry?

Hi,

I'm really interested in your module, looks good.
Do you think it would be possible to have a drop down selection list of existing zipcodes, by state for instance, instead of free user entry?
Would be good to be able to select this from the administration menu. It would avoid the user to select non defined zipcodes. Also it would help him, if for instance he has in the drop down list both the zipcode and corresponding city. In case he does not know the zipcode, he could choose it by the city..

Well, just suggesting..
Thanks a lot anyway for this nice new module!

Matt