Hi, there

I,ve searched for a couple of hours and have seen an awful lot of webpages this day, still i can not find the answer to, i think, a quite simple question.
First of all, my scripting skills are quite poor. I'm very willing to learn and i am determined to get my question fixed. I am not asking for a complete script, just lokking for some handles and een kick in the right direction.

What's my "problem":
For my website, i want a kind of postal code check.
When someone fills in his postalcode and submitted this, he needs to be directed to another page, with information regarding the region that belongs to his postal code.

I have a wild guess how this should work, but please, correct me if i'm (probably very) wrong:

I will have to create a form, with only one field: postal code.
The "action"of that form has to point to a javascript.
That script compares the value of the filled in postalcode to some document (txt, xml ??) or database.
If the two value match, the user will be directed to another url.

Is there someone who can gives me a push in the right direction ?

Thanks in advance,
The Hague, Netherlands