关于消息的问题！高手帮忙！

[bluesage]

一个BUTTON1按下后，向另一个BUTTON2发送了一条自定义消息，BUTTON2的接受消息的过程怎么写？下面代码中我想让BUTTON2响应，我觉得应该是可以。
unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;
const
MYMESSAGE = WM_USER+200 ;
type
TForm1 = class(TForm)
Button1: TButton;
Button2: TButton;
procedure getmess(var msg : TMessage); message MYMESSAGE ;
procedure Button1Click(Sender: TObject);

private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;

implementation

{$R *.dfm}
procedure tform1.getmess(var msg : TMessage) ;
begin
showmessage('i have got it');
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
postmessage(form1.Handle ,MYMESSAGE,0,0);
end;

end.

[xzgyb]

unit Unit1;

interface

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

const
MYMESSAGE = WM_USER+200 ;

type
TMainForm = class(TForm)
Button1: TButton;
Button2: TButton;
procedure FormCreate(Sender: TObject);
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
FOldWndProc: TWndMethod;

procedure NewWndProc(var Msg: TMessage);
public
{ Public declarations }
end;

var
MainForm: TMainForm;

implementation

{$R *.dfm}

procedure TMainForm.FormCreate(Sender: TObject);
begin
FOldWndProc := Button2.WindowProc;
Button2.WindowProc := NewWndProc;
end;

procedure TMainForm.NewWndProc(var Msg: TMessage);
begin
if Msg.Msg = MYMESSAGE then
ShowMessage('I have got it')
else
FOldWndProc(Msg);
end;

procedure TMainForm.Button1Click(Sender: TObject);
begin
SendMessage(Button2.Handle, MYMESSAGE, 0, 0);
end;

end.

不过没什么必要

[bluesage]

我在测试DLL的时候，我改变了DLL中函数的参数，可是怎么更新测试程序啊？？