Its not difficult.
Set the pointer over the yellow bar in the volume clip.
Move the pointer to the start of the clip and CTRL click the yellow line. (You have set a keyframe)
Now move the pointer to a second or two into the clip (or where ever you wan tthe volume to be normal)
Now move the pointer over the first keyframe and drag the frame down to the bottom of the clip (or until the info box reads 0 (zero) decibels).
Simple as that.
Good package incidentally!
COMPAQ something or other with 500Gb Boot Disk, 1Tb external Firewire Disk, 4Gb Memory and a super duper sound card, 19" TFT Monitor etc etc etc
Sony TRV33e : Sony TRV310e : Canon XM2
Sony Vegas Studio editions to v11
Remember, there is always more to learn than there is to teach.