5-Button mouse trigger(back and forward)?

[Gintaras]

#X1 should work. If does not work, maybe mouse software maps these buttons to keys. Usually it is configurable. Or, try to set keyboard triggers for that keys. In Properties, select Keyboard, click Hot-key field, and click 4-th or 5-th mouse button. If it is mapped to a key, this should set trigger for that key, eg (166).