I answered this in your Vegas Video forum post, but here it is again.

"If you have Sound Forge, you can do this by right clicking on an event in Vegas, and select "Open Copy in Sound Forge". Within Sound Forge, you would use EFFECTS>PITCH>BEND and this will put a velocity envelope over the audio you have selected. Save the changes in Sound Forge and then audition it in Vegas."

Vegas doesn't do this. The only way it could be done in Vegas is if you got an automatible Pitch shift or Timestretch plugin, which Vegas doesn't come with. It does have a timestretch plugin, but it's not automatible. The only other way to do it, is to cut the audio into many smaller event segments, and then you would have to use the Vegas timestretch options for each individual event, which won't sound as well as having something that is continuous like a plugin.