Fechar janela que eu já tenho o Handle: código falha...

Function EnumWindowsProc (Wnd: HWND; lb: TListbox): BOOL; stdcall;
var
   caption: Array [0..128] of Char;
begin
   Result := True;
   if IsWindowVisible(Wnd) and ((GetWindowLong(Wnd, GWL_HWNDPARENT) = 0) or
   (HWND(GetWindowLong(Wnd, GWL_HWNDPARENT)) = GetDesktopWindow))and
   ((GetWindowLong(Wnd, GWL_EXSTYLE) and WS_EX_TOOLWINDOW) = 0) then
   begin
      SendMessage( Wnd, WM_GETTEXT, Sizeof(caption),integer(@caption));
      lb.Items.AddObject( caption,TObject( Wnd ));
   end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
   ListBox1.Items.Clear;
   EnumWindows( @EnumWindowsProc, integer( listbox1 ));
end;


procedure TForm1.Button2Click(Sender: TObject);
var
   Contador : Integer;
   Janela   : hWND;
   Nome     : String;
begin
   For Contador := 0 To (ListBox1.Items.Count-1) Do
   Begin
      Nome := Trim(Copy(ListBox1.Items.Strings[Contador],1,6));
      If Nome <> ´Listar´ Then
      Begin
         Janela:= FindWindow(nil, PChar(ListBox1.Items.Strings[Contador]));
         SendMessage(Janela, WM_CLOSE,0,0);
      End;
   End;

end;