In the script, use a handle.

Example:

Code:

---

function playSomeSound()
{
   if(snd_playing(mySnd) != 1)
   {
       mySnd = snd_play(aSound,25,0);
   }
   else
   {
      return;
   }
}
  

---

Now everytime playSomeSound() is called, it first checks if the sound is playing (snd_playing). If not, it plays the sound. If the sound is playing, it simply returns.