Fade sound out

All the links and tips around here show how to fade a sound out, but they all involve buttons or sliders. Is there a way in a frame-AS to start a 5 second fade out on a sound that has been loaded in a new _level and is activated with:

MySound = new Sound(this);
MySound.start(0, 1);

I can set the overall volume here, but fade it out after it’s been playing for 30 seconds…