I think you have a problem if it’s got to be a break message.
1. It can only be sent while the user is signed in
2. It must be sent to a workstation — not a user
TATOOL solves issue 2 SNDBRKACT TAATOOL
But you will need to determine if the user is on line or hold the request until the user is on-line
Recommend a regular message or e-mail?
See http://itknowledgeexchange.techtarget.com/itanswers/send-a-break-message-to-multiple-users/?asrc=EM_UGT_5673743&uid=5669772 for a similar question.
You can send break messages programatically, but I’m not sure what happens if they are signed off when using my method.