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procedure SetLED(Key: Byte; MakeOn: Boolean);
var
  KS: TKeyboardState;
  OnOrOff: Boolean;
begin
  GetKeyboardState(KS);
  OnOrOff:= KS[Key] <> 0;

  // Wenn Status vom gewünschten abweicht
  if (OnOrOff xor MakeOn) then
  begin
    // Je nach Plattform / Key unterschiedliche Strategien
    if (Win32Platform = VER_PLATFORM_WIN32_NT)
      or (Key <> VK_NUMLOCK) then
    begin
      // Tastendruck simulieren
      keybd_event(Key, $45, KEYEVENTF_EXTENDEDKEY, 0);
      keybd_event(Key, $45, KEYEVENTF_EXTENDEDKEY or
        KEYEVENTF_KEYUP, 0);
    end
    else
    begin
      // Gewünschten Status per Setkeyboardstate setzen
      KS[Key]:= Ord(MakeOn);
      SetKeyboardState(KS);
    end;
  end;
end;					

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procedure TForm1.Button1Click(Sender: TObject);
begin
SetLED(vk_NumLock,True);
SetLED(vk_Scroll,True);
SetLED(vk_Capital,True);
end;					

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procedure TForm1.Edit1KeyDown(Sender: TObject; var Key: Word;
  Shift: TShiftState);
begin
listbox1.items.add(pchar(inttostr(key)));
listbox1.topindex:=listbox1.items.count-1;
end;