Hello Thomas,
You should just need to make sure that your sample has a loop in it (i.e. is sustaining), and create a Stop entry with:
SustainingSoundEffect_RankID
SustainingSoundEffect_MIDINoteNumber
... set to point to your Zimbelstern rank/note. (Don't create any StopRank entries for that Stop.)
Then whenever the user has that stop turned on the note will sound, and continue sounding until he/she turns the stop off again.