Thanks to SOB and Sylar for all the help.

I have found a solution that works for me. I will post it here in case it may be of help to others.

Code:
function ContactEvent()
{
  switch (event_type)
  {
    case EVENT_BLOCK: 
    {
      c_trace (me.x, target, IGNORE_ME|IGNORE_PASSABLE|IGNORE_MAPS|IGNORE_MODELS|IGNORE_SPRITES|USE_BOX|SCAN_TEXTURE);
      if (tex_flag3)
        snd_play(sndA,100,0);
      else
        if (tex_flag4)
          snd_play(sndB,100,0);
    }
  }
}


No more Programming Languages please, my head is a filled up! wink