Hallo Heike,
das sollte kein Problem sein. Es gibt eine je entsprechende Konstante für ON und OFF.
Hier die nötigen Code Fragmente.
Private Declare Function SendMessage Lib "user32" Alias _
"SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
Private Const WM_SYSCOMMAND = &H112&
Private Const SC_MONITORPOWER = &HF170&
Private Const MONITOR_ON = -1&
Private Const MONITOR_OFF = 2&
Call SendMessage(Me.hwnd, WM_SYSCOMMAND, SC_MONITORPOWER, ByVal MONITOR_OFF)
Call SendMessage(Me.hwnd, WM_SYSCOMMAND, SC_MONITORPOWER, ByVal MONITOR_ON)
Gruß Frank