HOWTO: Toggle the NUM LOCK, CAPS LOCK, and SCROLL LOCK Keys

   /* Compile options needed:
   */ 

   #include <windows.h>

   void SetNumLock( BOOL bState )
   {
      BYTE keyState[256];

      GetKeyboardState((LPBYTE)&keyState);
      if( (bState && !(keyState[VK_NUMLOCK] & 1)) ||
          (!bState && (keyState[VK_NUMLOCK] & 1)) )
      {
      // Simulate a key press
         keybd_event( VK_NUMLOCK,
                      0x45,
                      KEYEVENTF_EXTENDEDKEY | 0,
                      0 );

      // Simulate a key release
         keybd_event( VK_NUMLOCK,
                      0x45,
                      KEYEVENTF_EXTENDEDKEY | KEYEVENTF_KEYUP,
                      0);
      }
   }

   void main()
   {
      SetNumLock( TRUE );
   }