How to configure repeating alarm?

I want to generate repeating alarm when e.g. SMTP service fails on my server. How to do it? If I create notification with sound alarm and I set “repeat count”, the sound is plaing just “repeat count” times. But if the service is back on-line, I would like to stop the alarm playing the sound file (but it is continuing until “repeat count” times played).
Simple, I would like to create alarm that is playing an alarm sound until the service is back online or until I switch it off manually.