Private Declare Function ExitWindowsEx Lib "user32" _
                       (ByVal uFlags As Long, _
                        ByVal dwReserved As Long) As Long
 
Private Declare Function LockWorkStation _
Lib "user32.dll" () As Long
 
Const EXW_LOGOFF = 4
Const EXW_REBOOT = 2
Const EXW_SHUTDOWN = 1
 
Private Sub cmdOk_Click()
Dim strIndex As String
strIndex = cmbAuswahl.Text
Select Case strIndex
    Case "Herunterfahren":
        ExitWindowsEx EXW_SHUTDOWN, &HFFFF
        'Shell "shutdown.exe -s"
    Case "Neu Starten":
        ExitWindowsEx EXW_REBOOT, &HFFFF
        'Shell "shutdown.exe -r"
    Case "Abmelden":
        ExitWindowsEx EXW_LOGOFF, &HFFFF
    Case "Computer sperren":
        LockWorkStation
    Case Else
End Select
End Sub