It's certainly possible, but I don't have any examples to provide you. A form can be set up to submit a requuest to a web server, either using a standard HTTP Post or via SOAP. So either you have to program a web server to return a response (e.g., an FDF) or find an existing web service that allows the type of query you need.
There are many different web based services for finding postal codes. The US Postal service has a web site here: http://zip4.usps.com/zip4/welcome.jsp
Also, do a google search on "zip code web service". You'll find several links.
Actually, the LiveCycle scripting model has a FormCalc function that will make an HTTP request and acquire the returned HTML. So I'm pretty sure you could put zip code acquisition code into a LiveCycle form, but I haven't tried it.
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Thanks so much for your time George & Thom. That is all above my level of expertise right now but, I'll tackle it down the road as I learn more about scripting.
Have a great week!