[NumLock]

функция:

Код:

function NeedKeyboardLayout: Cardinal;
var
  hForegroundWindow: THandle;
  idProcess: DWORD;
begin
  hForegroundWindow:=GetForegroundWindow;
  idProcess:=GetWindowThreadProcessId(hForegroundWindow);
  Result:=LOWORD(GetKeyboardLayout(idProcess));
end;

использование в таймере, к примеру:

Код:

procedure TForm1.Timer1Timer(Sender: TObject);
var
  kbl: Cardinal;
begin
  kbl:=NeedKeyboardLayout;
  Label1.Caption:=IntToStr(kbl);
  case kbl of
    $409: Label2.Caption:='en';
    $419: Label2.Caption:='ru';
    else Label2.Caption:='oops';
  end;
end;