[otrs] Locking to agent

Hi, I would like to add a rule in example procmail to add a header that OTRS picks up and lock the specific case to a specific agent.. for example.. Incoming mail with "Subject: Att. John" then I'd like to add a header to the mail that OTRS then sees and lock the specific incoming mail to the Agent "John".. is this possible or can it be done in some other way.. like GA ? Regards, Patrik