Fichier /etc/X11/imwheel/startup.conf:
# Configuration file for setting imwheel startup parameters.

# Set this to "1" to make imwheel start along with your X session.
IMWHEEL_START=1

# Specify the command line parameters to pass to imwheel.
# Simply uncomment the bottom line, and if necessary replace
# the default options with your own. A button spec of "0 0 8 9"
# will grab the thumb buttons of most mice. "0 0 0 0 8 9" should
# work for mice with a scroll wheel with two axes. Keep in mind
# that each button number must be separated by a space.
IMWHEEL_PARAMS='-b "0 0 7 6 8 9"'

Fichier /etc/X11/xorg.conf:
Section "InputDevice"
        Identifier      "Configured Mouse"
        Driver          "evdev"
        Option          "Dev Name"              "Dell Premium USB Optical Mouse"
        Option          "Dev Phys"              "usb-0000:00:1d.0-1/input0"
        Option          "Device"                "/dev/input/event1"
        Option          "Buttons"               "9"
        Option          "ZAxisMapping"          "4 5"
        Option          "Emulate3Buttons"       "no"
        Option          "SendCoreEvents"        "true"
        Option          "ButtonMapping"         "1 2 3 8 9"
        Option          "HWHEELRelativeAxisButtons" "6 7"
EndSection

Fichier /home/votreUser/.imwheelrc:
".*"
None, Left, Control_L|C
None, ExtBt7, Control_L|V
None, Right, Control_L|X
None, Thumb1, Alt_L|Left
None, Thumb2, Alt_L|Right