sad69: Thanks for the advice, after reading your response I did a bit more searching and found this script http://www.yxscripts.com/cs/chainedselects.html
which I've decided to use instead which does almost everything I need. Now I've had this working fine, then changed a few things and it stopped working, and for the life of me I can't figure out what I've changed. I'm getting the following error message now.
Error: 'document.forms.0.field1' is null or not an object
What does that error message mean?
I can post the whole code if anyone wants to help me but the rules state that sort of question isn't allowed.