To get your Wheel Mouse to work with all the buttons, including the back forward buttons on the left side of the mouse:

For Xfree (/etc/X11/XF86Config)
Section "InputDevice"

        Identifier      "Intellimouse"
        Driver          "mouse" 
        Option          "Protocol"              "IMPS/2"
        Option          "Device"                "/dev/usbmouse"
        Option          "Buttons"               "7"
        Option          "ZAxisMapping"          "6 7"

( If you do not want to bother with back/forward buttons on the side of the mouse then you can use Option ZAxisMapping" "4 5" and remove the Option "Buttons" "7" line entirely, as well as ignore the rest of this how-to. )

To remap the buttons (~/.xsession (or whatever other startup script you are using)
#remap the mouse pointer buttons
xmodmap -e "pointer = 1 2 3 6 7 4 5"
For the back / forward buttons

Install xvkbd |

In your settings for your keybinds/mousebinds in your WM or DE:

set mouse button 6 to:
xvkbd -xsendevent -text "\[Alt_L]\[Left]"

set mouse button 7 to:
xvkbd -xsendevent -text "\[Alt_L]\[Right]"

(NOTE: These settings will work even if you do not set up the back/forward buttons)