Declarations

#If Win32 Then

    Private Declare Function SendMessage Lib "user32" _
    Alias "SendMessageA" (ByVal hWnd As Long, ByVal wMsg _
    As Long, ByVal wParam As Long, ByVal lParam As Long) _
    As Long

    Const WM_SYSCOMMAND = &H112&
    Const SC_SCREENSAVE = &HF140&

#Else

    Private Declare Function SendMessage Lib "User" _
    (ByVal hWnd As Integer, ByVal wMsg As Integer, ByVal _
    wParam As Integer, lParam As Any) As Long

    Const WM_SYSCOMMAND = &H112
    Const SC_SCREENSAVE = &HF140&

#End If

Code

To start the screen saver, use the following code:

Dim result As Long
result = SendMessage(Form1.hWnd, WM_SYSCOMMAND, SC_SCREENSAVE, 0&)