Multiple ambient sounds?

I have been talking with Maxi about the 2 different Vierville ambient sounds, and we were wondering if it's possible to make it alternate between the 2 sound files, rather than just play 1. Anybody know how to do that?

I know I said that already, but you can delay sounds.
For calculated switching on/off I can only imagine coding, which doesn't work in MP (you know, there are triggerable sounds in the campaigns which are coded).