Hmm. Tricky one...
You could create two triggers. One for East pressent and one for West pressent.
On the west trigger put westsound=True
On the east trigger put eastsound = True
The create the script.
#check
?Westsound : goto "West"
?Eastsound : goto "East"
~1
goto "Check"
#West
playsound "westsound"
goto "Check"
#East
Playsound "Eastsound
goto "Check"
Don't know if this script is so good, but at least you'll se what I'm getting to...