Our users create tickets with specific 7 digit OTS #'s.  These OTS #'s are entered into a field on the ticket called "Artwork OTS Number".

Many of our users will create a new ticket with that same 7 digit OTS # and append it with -c1, -c2, etc. when there is information to be added, instead of adding that information to the current ticket.  Is there a way to create a rule that will limit users to one open ticket per 7 digit OTS #, even if the user attempts to append the number?

Thanks.