Mouse buttons mouse functions?
I can only speak for Logitech mice as they are the only mice I have ever used. When you install the drivers for a Logitech mouse, you also install their mouse/keyboard software called SetPoint. With the SetPoint software, you can remap most if not all the keys of the mouse to either a specific task (Back, Document Flip, etc) or to a key (F11, Ctrl-T, etc).
I am currently using a Logitech G700 mouse which has 7 extra buttons. I have them mapped to various game hot keys like V for dodge, 6 for my heal and so on. I could also remap the left and right button and the wheel if I wanted to but they are working fine as they are.
you have to set the commands in-game to keys on your keyboard and then map your mouse buttons to those keys.
Northern Shiverpeaks
The limitation is with Windows, not the mouse. Windows only recognizes 5 logical mouse buttons: left, right, middle, left-side, right-side (I’m not 100% sure, but I think Windows XP might not recognize the side buttons and only uses 3 logical buttons). Additional buttons won’t get picked up by Windows unless you use your mouse’s custom drivers to map the additional buttons to specific keystrokes.
So to answer your question: when shopping for a mouse, make sure it includes software that allows you to remap mouse buttons to keystrokes and/or macros.