AJAX ComboBox - required field validator

I want to put validation on a ajax combobox to ensure user selects/enters a value.

I've tried using a the standard required field validator which doesn't work. So I would like to do the validation using javascript/jquery.

Not sure how to approach. When I look at how the combo box is rendered, it appears as a unordered html list. There is also a hidden field but this always seems to be set to 0.

So is it possible to do this validation client side.

I've read so many posts about this but I havn't got an answer yet.

Am I on the wrong path here? Any ideas?

Thanks