Client-side dynamic drop down menu?

Does anyone have or know where i can find a working javascript/VBscript that will allow me to have a drop down menu that loads its values based on the selection in another drop down menu which in turn gets its value from another dropdown menu? Just as an example to explain my question...

Lets say I wanted a menu that listed manufacturer:

Ford, GM, Chrystler.

then based on that model:

F150, F250, F350, Superduty, Mustang, etc...

then based on that engine type:

4.2V6, 5.4V8, 5.8V8, 6.2D, etc...

How do I do that? I've made a javascript that seemed to work, then I put it in a form and it doesn't work anymore. I can't figure out why, or how to fix it yet. I'm getting pretty familar with HTML, Javascript, HTML DOM. I don't have access at this time to PHP, ASP, MySQL... I've avoided databases by using arrays. Thank you.