I know how to turn on/off all monitors by using user32.dll.

```
SendMessage(HWND_BROADCAST, WM_SYSCOMMAND, SC_MONITORPOWER, (LPARAM) -1);
SendMessage(HWND_BROADCAST, WM_SYSCOMMAND, SC_MONITORPOWER, (LPARAM)  2);

```

But I want to turn on/off only single one.