Easy enough, use the system choose parameter.
If player overlap door 1 then set variable randomDoor Choose (1 , 2, 3)
If randomDoor = 1 then spawn player at Door 1
if randomDoor = 2 then spawn player at Door 2
etc...
Sorry, I'm at work. If you need a Capx example then let me know. I'll do it late tonight or tomorrow morning (eastern time).