frm1 code:

  unit frm1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ToolWin, ComCtrls, ExtCtrls, Buttons, Menus;

type
  TForm1 = class(TForm)
    ScrollBox1: TScrollBox;
    BitBtn1: TBitBtn;
    ToolBar1: TToolBar;
    ToolButton1: TToolButton;
    ToolButton2: TToolButton;
    ToolButton3: TToolButton;
    MainMenu1: TMainMenu;
    f1: TMenuItem;
    ds1: TMenuItem;
    df1: TMenuItem;
    df2: TMenuItem;
    df3: TMenuItem;
    PopupMenu1: TPopupMenu;
    N1: TMenuItem;
    N2: TMenuItem;
    procedure Button1Click(Sender: TObject);
    procedure BitBtn1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

    uses
 frm2;

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
begin
  form2:=Tform2.Create(self);
   form2.Show;
end;

procedure TForm1.BitBtn1Click(Sender: TObject);
begin
  form2:=Tform2.Create(self);
  form2.Width:=700;
  form2.Height:=500;
  form2.top:=0;
  form2.Left:=175;
   form2.Show;
end;

end.

-------------------------
frm2 code:

unit frm2;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls;

type
  TForm2 = class(TForm)
    Panel1: TPanel;
    Button1: TButton;
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
    procedure FormCreate(Sender: TObject);
    
  private
    procedure WMGetMinMaxInfo (var Message:TWMGetMinMaxInfo);
              message WM_GETMINMAXINFO;
  public
    { Public declarations }
  end;

var
  Form2: TForm2;

implementation

{$R *.dfm}


Procedure Tform2.WMGetMinMaxInfo(var Message: TWMGetMinMaxInfo);
 begin
  with Message.MinMaxInfo^ do
   begin
     ptMaxSize.X := 700;//最大化时候的宽度
     ptMaxSize.Y := 500;//最大化时候的高度
     ptMaxPosition.X :=100;//最大化时作上角横坐标
     ptMaxPosition.Y :=175;
   end;
   Message.Result := 0; //告诉WINDOWS 改变了 minmaxinfo
   inherited;
   end;

procedure TForm2.FormClose(Sender: TObject; var Action: TCloseAction);
begin
  action:=cafree;
end;

procedure TForm2.FormCreate(Sender: TObject);
begin

end;

end.
-----------------------
frm3 code:

unit frm3;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ExtCtrls;

type
  TForm3 = class(TForm)
    Panel1: TPanel;
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form3: TForm3;

implementation

{$R *.dfm}

procedure TForm3.FormCreate(Sender: TObject);
begin

end;

end.
------------------------------------

问题：
  frm1主窗体   设置为主窗体
  frm2子窗体         child
   frm3子子窗体 设置为什么呢？
才能在frm2中的按钮点了之后，出现frm3？

谢谢！