ciao guys

I am trying to prepare a sort of effect machine to be used during live events
I will usa an Akai APC MINI as interface, and i would like to associate to a number of buttons some audio effects

My problem is:
- When I press the button the sound have to start
- When I re-press the button the sound have to stop

easy with the playpause command, BUT

My problem is: how can I manage the SetVolumeFade option?
i would like to have a fade in effect, and a fade out
i can't know in advance the duration, think to applauses, laughts, a jingle, and so on
i will prepare samples may be 3 minutes long, and may be in loop, so will be easy to manage

i can only do one of the two things, set volumefade in or out, but i can't see a sort of toggle

Can someone help me?

Ciao again and thank you