Is there a way to add a custom RCS keyword in Perforce?

Perforce supports various RCS keywords including $file$ and $version$. Is there a way to add a custom RCS keyword?

I want to create a custom k开发者_StackOverfloweyword so that when the file is checked in, Perforce will replace the keyword with a custom string.

e.g.
from:    $customString$
to:      This is a custom message

No, but I'd imagine its possible to write a trigger script to do this for you if you so wish.

http://www.perforce.com/perforce/doc.current/manuals/cmdref/triggers.html

Perhaps if you explain further what you are tring to achieve their might be some suggestions.