Automated address selection feature in a contact/order form

Hi all,

I have recently built a site (not currently live) and I have been asked to see if I can implement an automatic address finder within the current order form which was created with standard xhtml/css.

Currently a user has to enter the first line of there address manually then proceed down to the next input field and enter the next part of there address etc etc, but on most corporate websites, you can normally just fill out your postcode/zipcode, and press enter and you get a drop down menu with all address`s including house names or numbers that relate to that particular postcode/zip - I undertand that this will involve sever side scripting of some sort and possibley even a database ?

Its probably out my league for trying to implement, but after several failed attempts at trying to find how to or where to start, I thought I`d drop a post on here and pick any brains of “technovangelists”

Look forward to hearing from anyone on this matter and apologies if this has been posted in the wrong forum.