有没有办法向一组自定义的非可视化类广播自定义的消息？高手来帮忙啊

我的程序如下
unit Unit1;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ExtCtrls, Unit2, StdCtrls;type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
    FPluginRegistry : TPluginRegistry;
  public
    { Public declarations }
  end;var
  Form1: TForm1;implementation{$R *.dfm}procedure TForm1.FormCreate(Sender: TObject);
begin
   FPluginRegistry := TPluginRegistry.Create;
   RegisterWindowMessage('WM_DESERIALIZATION');
end;procedure TForm1.Button1Click(Sender: TObject);
begin
  //如果我用这句就可以接收到自定义的消息
//  PostMessage(FPluginRegistry.WindowHandle,WM_DESERIALIZATION,0,0);
  //如果用这句就不行，怎么样才能实现广播呢？
  PostMessage(HWND_BROADCAST,WM_DESERIALIZATION,0,0);
end;end.
unit Unit2;interfaceuses Classes, Windows, Messages,Dialogs;const
  WM_DESERIALIZATION = WM_USER + 100; type
  TPluginRegistry = class(TPersistent)
  private
    FWindowHandle: HWND;
    procedure WndProc(var Msg: TMessage);
  protected
    procedure ProcessSaveProperty; virtual;
  public
    constructor Create;
    destructor Destroy; override;
    property WindowHandle : HWND read FWindowHandle;
  end;implementationuses Forms;
{ TPluginRegistry }constructor TPluginRegistry.Create;
begin
  inherited Create;
  FWindowHandle := Classes.AllocateHWnd(WndProc);
end;destructor TPluginRegistry.Destroy;
begin
  Classes.DeallocateHWnd(FWindowHandle);
  inherited;
end;
procedure TPluginRegistry.ProcessSaveProperty;
begin
  Showmessage('Received');
end;procedure TPluginRegistry.WndProc(var Msg: TMessage);
begin
  with Msg do
    if Msg = WM_DESERIALIZATION then
      try
        ProcessSaveProperty;
      except
        Application.HandleException(Self);
      end
    else
      Result := DefWindowProc(FWindowHandle, Msg, wParam, lParam);
end;end.