Section "InputDevice"
    Identifier "Keyboard1"
    Driver "kbd"
    Option "XkbModel" "microsoftinet"
    Option "XkbLayout" "us,el"
    Option "XkbOptions" "grp:alt_shift_toggle,grp_led:scroll,compose:rwin"
EndSection

avl adds:  (mine looks like this...    perhaps you can play aroud with that)
Section "InputDevice"
        Identifier      "Generic Keyboard"
        Driver          "kbd"
        Option          "CoreKeyboard"
        Option          "XkbRules"      "xorg"
        Option          "XkbModel"      "pc105"
        Option          "XkbLayout"     "de,gr"
        Option          "XkbOptions"    "lv3:ralt_switch,grp:shift_caps_toggle,grp_led:scroll"
        Option          "XkbVariant"    "nodeadkeys,extended"
EndSection