Volumouse allows you to use your mouse scroll wheel to control the volume on your computer. It lets you set up rules as to when the scroll wheel will affect the volume. Example rules would be: when holding down a certain key, when certain programs (media player, iTunes, RealPlayer, etc) have the focus, the cursor is over certain parts of the screen. If any of the rules are met, you can then use the scroll bar to control the volume. If the rules are not met, the scroll wheel behaves normally. You can also control the details of what audio channel is being controlled and the sensitivity of the adjustments. This program is free.