SOUND*snd1="shdfkdh.wav";
SOUND*snd2="shdfkfsddh.wav";
SOUND*snd3="shdfksdffddh.wav";

function playrandomsound()
{
   random_seed(0);
   wait(1);
   var i=random(2);
   switch(i)
   {
       case 0:
       snd_play(sound1...);
       case 1:
       snd_play(sound2...);
       case 2:
       snd_play(sound3...);
   }
}