delphi 添加系统菜单，点击新菜单没有反应的问题

program Psysmenu;
uses
  Forms,
  Sysmenu in '\SYSMENU.PAS' {Form1};

{$R *.RES}
begin
  Application.CreateForm(TForm1, Form1);
  Application.Run;
end.

unit Sysmenu;

interface
uses
  SysUtils, WinTypes, WinProcs, Messages, Classes, 
  Graphics, Controls,Forms, Dialogs;
type
  TForm1 = class(TForm)
        procedure FormCreate(Sender: TObject);
  private
      procedure  user_sysmenu(var msg:twmmenuselect);
                               message wm_syscommand;

  public
        { Public declarations }
  end;
var
  Form1: TForm1;
implementation
{$R *.DFM}

procedure  TForm1.user_sysmenu(var msg:TWMMENUSELECT);
begin
   if msg.iditem=100 then
      showmessage('     响应系统菜单!')
      { 也 可 以setwindowpos()来实现处于最前端功能}
   else
      inherited;     { 作缺省处理,必须调用这一过程}
end;

procedure TForm1.FormCreate(Sender: TObject);
   var hmenu:integer;
begin
   hmenu:=getsystemmenu(handle,false);
   {获取系统菜单句柄}
   appendmenu(hmenu,MF_SEPARATOR,0,nil);
   appendmenu(hmenu,MF_STRING,100,'加入系统菜单');
   {加入用户菜单}
end;
end.program Psysmenu;
uses
  Forms,
  Sysmenu i