how to select from two required fields

I am not sure I am expalining this correctly. I have this form:
http://www1.tau.ac.il/~maxv/law-lib/index.php?option=com_chronocontact&chronoformname=direct_service
I want the user to fill out either details for a book or an article, whichever he chooses the title should be a required field.
So if the user wants a book, the title for the book is a required field and then he doesn't have to fill any details about an article and vice versa.

Thanks,

Hava

this needs a custom JS code, Bob has written one here in the last few hours, try to look for it in the forums (HOW to/ Questions)!

Max

do you mean this thread http://www.chronoengine.com/forums.html?cont=posts&f=5&t=12259?

yes