Thanks johny10151981.

That certainly looks like something I could try out. However, ideally I would still like a solution that doesn't include any extra options or clicks - something that does the checking in the background without the user having the think about it.

Hello,

I have a form that has a series of five simple drop-down lists containing a few options each.

For the purposes of my form only one option from one of the lists should be selected at submission. So, as I see it, I need a way of either:

(1) validating on submission that only one of the lists has been used. If no options are selected from any of the lists, or options from more than one lists have been selected,...