Need (A:HSI CDI NEEDLE VALID,bool) to play sound only 1 time

I have a gauge to detect the events, but I need to know how to play the sound -ONLY- ONE time. The event stays up for a while, so it keeps repeating the sound.For instance using part of my gauge below to detect when the Glideslope Becomes active, usually about 24 miles from touchdown when it detects the NAV1 (ILS) frequency.--if{ (A:HSI CDI NEEDLE VALID,bool) if{ 1 (>L:snd_2,enum)Big picture is I'm just trying to play sounds for (GLIDESLOPE ACTIVE), (LOCALIZER ALIVE), (GLIDESLOPE ALIVE), and (GLIDESLOPE CAPTURED) and for them to play just one time.Thanks in advanceLKL