weeks - 10:28 pm on Apr 15, 2010 (gmt 0)
This is going to take some programming, of course. And it might not be worth it.
Also, think about this...
You know how you ask people twice to enter say, their password? People get it wrong. It's a good check to ask for this backup.
Even if you're not mailing them anything, but building a db, it's a good check to enhance the info's accuracy.
Now, if you are going to be mailing people stuff, you need to check out the USPS database where they'll make labels for you and such. A better investment would be to create an interface with their program.
Drill down deep into the postal service's web site for businesses that mail. And, of course, check out the other shippers web sites as well.