I'm hoping someone can point me in the right direction - I've been searching for ages with no success and haven't really much idea where to look:

I have a form with two drop-down boxes, where the content of the second needs to be dependent on the option chosen in the first

eg if the first dropdown box is 'countries' and the second is 'states', and the user chooses USA in the first dropdown box, they should only see USA states in the second box.

There isn't a high number of choices available to the user so the detail can be in a database or in the file itself with no problem.

All pointers where I start are very welcome