Failing a transaction in a scrip

Hi All,
I’d like to keep users from replying to closed tickets. So far
I’ve disabled the scrip that re-opens the closed tick, but I’d also like
to give an error if someone tries to reply to it.
Is there any way to tell RT to abort a correspond transaction
if certain criteria are met? (In this case, the ticket is closed)
Thanks for the help.

Erek Dyskant
Server Administrator