probably function buttin usually marked by FN in a square in the same colour writing, lower left corner of keyboard, however, i've never been able to use a multi key command with the FN key required (as in your case it would be ctrl+alt+FN+shift) as the depressing of the FN key seems to boot me out of they key sequence required, alternativly, you could try to use a USB external keyboard with a pause/break key