procedure TForm1.N11Click(Sender: TObject);
begin
  Form2.Free;
  Form2 := TForm2.Create(application);
  Form2.FormStyle := fsMDIChild;
  Form2.Show;
  SendMessage(Form2.Handle,WM_SYSCOMMAND,SC_MAXIMIZE,0)
end;

procedure TForm1.N21Click(Sender: TObject);
begin
  Form3.Free;
  Form3 := TForm3.Create(application);
  Form3.FormStyle := fsMDIChild;
  Form3.Show;
  SendMessage(Form3.Handle,WM_SYSCOMMAND,SC_MAXIMIZE,0)
end;

    if ClassType = TCustomForm then begin
      if AName = 'MAXIMALIZE' then begin
        if Application.MainForm.FormStyle = fsMDIForm then begin
          if Assigned(Application.MainForm.ActiveMDIChild) and (Application.MainForm.ActiveMDIChild.WindowState = wsMaximized)
            then PostMessage(Application.MainForm.Handle, WM_MDIMAXIMIZE, TCustomForm(Instance).Handle, 0)
            else PostMessage(TCustomForm(Instance).Handle,WM_SYSCOMMAND,SC_MAXIMIZE,0)
        end
        else PostMessage(TCustomForm(Instance).Handle,WM_SYSCOMMAND,SC_MAXIMIZE,0);
      end else
    end else