[otrs] Note on unlocking a ticket

Hi all, it's easy to unlock a ticket by clicking on the unlock-link. But I think it should be better to force the agent to write a note that explains the unlock-reason (meaning the reasons why the agent can no longer active work on the ticket) and perhaps the next steps that have to be done). It's no problem to disable the unlock-button by ACLs, but how can a ticket be unlocked by the composing of a note. Any ideas? Bye, Alex