I don't know if this would fit your budget, but I have played around with the Sound Forge demo and IIRC, there are plugins that would allow you to do this pretty easily. You can get the demo and the plugins (demo versions available as well) at http://www.sonicfoundry.com
My favorite sound editor to use is Goldwave. The shareware version is free and does all the same stuff the full version does, except the shareware version limits you to do only so many functions per session. Check it out at http://www.goldwave.com