http://forum.kodi.tv/showthread.php?tid=122795

 

This will only work in Eden as earlier versions of XBMC didn’t allow you to configure mouse actions.

Press Windows-R and in the Run dialog type:

notepad „%appdata%\xbmc\userdata\keymaps\mouse.xml“

and click OK, and answer Yes when XBMC asks if you want to create a new file. Copy and paste the following into Notepad:

Code:
<keymap>
<global>
<mouse>
<wheelup>VolumeUp</wheelup>
<wheeldown>VolumeDown</wheeldown>
</mouse>
</global>
</keymap>