Helo!!

Thank you in advance!
My problem is this: I have figured out how to fade the
sound I add in a presentation in Powerpoint 10 but the fade only works for one
slide, the specific slide I add the sound to. If I choose to keep a sound for,
say, 3 consecutive slides, I add the sound to the first slide and alter the
duration and pick where to cut it. And it works fine. But if I want to have the
sound fading after the third slide, the fade doesn't work. It only does it if
the sound plays on one slide only; if it's meant to play for many slides and
then fade, the fade doesn't work.
Do you have any idea, if I can actually do
that in powerpoint 10?
(Windows XP)
Thank you!