Fade out sound object

Hello,

I have a sound object that I would like to have fade out. I have read how to fade a looping sound and how to fade a non-looping sound after a certain amount of time, but neither of these enable me to do what I want. I have an interactive piece with a non-looping sound that I want to fade when the viewer gets to a specific frame, regardless of how long the sound has played for. Anyone know how to do this?

Thanks in advance,

llyfre