I think this is all 19 combinations:
Code:
LCtrl
LCtrl   LShift
LCtrl   LAlt
LCtrl   LShift  LAlt
LCtrl   RShift
LCtrl   RAlt
LCtrl   RShift  RAlt
LCtrl   LShift  RAlt
LCtrl   LAlt    RShift

LShift
LShift  LAlt
LShift  RCtrl
LShift  RAlt
LShift  RCtrl   RAlt
LShift  LAlt    RCtrl

LAlt
LAlt    RCtrl
LAlt    RShift
LAlt    RCtrl   RShift
Please double check this because I'd like to know myself for sure.