Declare Function GetActiveWindow Lib "user32" () As Long
Declare Function PostMessage Lib "user32" Alias "PostMessageA" (ByVal hwnd As Long, ByVal msg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
Declare Function GetLastError Lib "kernel32" () As Long
Const WM_COMMAND = &H0111
Const ID_ELVISRUN_LOGIN = 35000

Sub Benutzerwechsel_Click()
	' Post a WM_COMMAND with ID_ELVISRUN_LOGIN to the main window
	Dim hwnd As Long
	hwnd = GetActiveWindow()
	If PostMessage(hwnd, WM_COMMAND, ID_ELVISRUN_LOGIN, 0&) = 0 Then
		MsgBox "PostMessage failed: " & GetLastError()
	End If
End Sub