Drop Down box Chained, PHP and MYSQL

Hi,
I am new to Jquery and Js i do understand the basic concept of programming as i usually develop with php

I have 3 drop down box

  1. contains car manufacturers
  2. contains car models
  3. contains car spec

the three are dependent [chained] and are all populated from the mysql db.

It works fine but as we all know to retrieve the values for combo box 2 and 3 i will have submit the form … I would rather do this in a Jquery way where i wont have to click submit after every form input.

I dont know how to use Jquery for this particular situation…
please send me some samples or even a link where i can understand

kind regards