A simple trigger sample loop object ?

Hi,
This should be really simple . I am doing a sound installation where an infrared sensor triggers a track when someone walks through a door. The thing is I dont want the track to restart every time someone walks into the room - ie if five people walk in t the same time I only want it triggered once until the track has finished playing, once the track has finished then and only then will the patch accept another input signal to trigger it.
IE subsequent input signals are ignored until the sample has finished playing , then the input signal can restart the sample . I know sfplay emits a bang when finished but has anyone any ideas how to implement it ? Im sure its very easy if you know how....
PS its an 8 channel track so I probably do need to use sfplay~