Сложный хук

program Template;
 
uses
  Windows, Messages;
 
var
  wClass: TWndClass;
  Msg: TMsg;
  Win: HWND;
 
function WindowProc(Win, Msg, WP, LP: Integer): Integer; stdcall;
var
  S: string;
begin
  case Msg of
 
    WM_COMMAND:
    begin
      Str(WP, S);
      SetWindowText(Win, PChar(S))
    end;
 
    WM_DESTROY:
      PostQuitMessage(0)
 
  end;
  Result := DefWindowProc(Win, Msg, WP, LP)
end;
 
 
BEGIN
  with wClass do
  begin
    lpszClassName:= 'asd';
    lpfnWndProc :=  @WindowProc;
    hbrBackground := 1;
    hCursor := LoadCursor(0, IDC_ARROW)
  end;
  RegisterClass(wClass);
 
  Win := CreateWindow(wClass.lpszClassName, 'Заголовок программы',
    WS_OVERLAPPED or WS_SYSMENU or WS_MINIMIZEBOX or WS_VISIBLE,
    400, 300, 340, 220, 0, 0, hInstance, nil);
 
  CreateWindowEx(0, 'Button', 'Кнопка 1', WS_VISIBLE or WS_CHILD,
    185, 170, 70, 20, Win, 1001, hInstance, nil);             // ID кнопки 1001
  CreateWindowEx(0, 'Button', 'Кнопка 2', WS_VISIBLE or WS_CHILD,
    260, 170, 70, 20, Win, 1002, hInstance, nil);             // ID кнопки 1002
 
  while GetMessage(Msg, 0, 0, 0) do
  begin
    TranslateMessage(Msg);
    DispatchMessage(Msg)
  end;
END.