2、在要实现的unit中定义一个私有方法

   procedure doMyMessage(var msg:TMessage);message WM_MyMessage;

3、实现这个私有方法

    procedure TForm1.doMyMessage(var msg:TMessage);

begin

  //

  if msg.Msg= WM_MyMessage then

    showmessage('好啊')

  else

    showmessage('不好');

end;

4、最重要 把这个消息广播出去 Form1.Perform(WM_MyMessage,0,0);

下面是实现的代码

unit Unit1;

interface

uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, StdCtrls;

const WM_MyMessage=WM_USER+$200;

type

  TForm1 = class(TForm)

    Button1: TButton;

    procedure Button1Click(Sender: TObject);

  private

    procedure doMyMessage(var msg:TMessage);message WM_MyMessage;

    { Private declarations }

  public

    { Public declarations }

  end;

var

  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.doMyMessage(var msg:TMessage);

begin

  //

  if msg.Msg= WM_MyMessage then

    showmessage('好啊')

  else

    showmessage('不好');

end;

procedure TForm1.Button1Click(Sender: TObject);

begin

   Form1.Perform(WM_MyMessage,0,0);

end;

end.