Turning off just the screen of a laptop or desktop pc programatically

Hi,
If you are trying to achieve this via a cross browser web application, this is not possible. In you want to create website that is limited to Internet Explorer, you can get your target done by using ActiveX.
However, even you manage to get this done, that will not work on Other Browsers and Operating systems.

Sorry that I didn't notice about Visual Basic 2013 in your question, here is an equivalent code in VB.NET 2013

' use SendMessage for synchronous call, wait until message is processed
Declare Auto Function SendMessage Lib "user32" (ByVal hWnd As Integer, ByVal wMsg As Integer, ByVal wParam As Integer, ByVal lParam As Integer) As Integer
' use PostMessage for asynchronous call, don't want to wait until message is processed
Declare Auto Function PostMessage Lib "user32" (ByVal hWnd As Integer, ByVal wMsg As Integer, ByVal wParam As Integer, ByVal lParam As Integer) As Integer

' turn off monitor
SendMessage(-1 /* HWND_BROADCAST */,  &H112 /* WM_SYSCOMMAND */, &HF170 /* SC_MONITORPOWER */, 2 /* MONITOR_OFF */)
' or
PostMessage(-1 /* HWND_BROADCAST */,  &H112  /* WM_SYSCOMMAND */, &HF170 /* SC_MONITORPOWER */, 2 /* MONITOR_OFF */)

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P.S.: Sorry that I haven't got the time to test the VB.NET, just quickly translated it on-the-fly.

You could use this:
https://www.experts-exchange.com/questions/28686918/vb-2013-command-to-turn-off-the-screen-but-not-the-pc.html

ps.  If you close a question of by accepting something that turns out NOT to work, just click the request a tention button rather rather than opening a new question.

Thanks to all Experts!