怎样使单击事件变为双击事件(50分)

TForm1 = class(TForm)
procedure FormClick(Sender: TObject);
procedure FormDblClick(Sender: TObject);
procedure FormCreate(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
Flag: Boolean;
end;

var
Form1: TForm1;
implementation
{$R *.DFM}
{ TForm1 }
procedure TForm1.FormClick(Sender: TObject);
begin
if Flag then
begin
ShowMessage (‘You click me!‘);
Flag := False;
end;
end;

procedure TForm1.FormDblClick(Sender: TObject);
begin
Flag := True;
FormClick(Self);
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
Flag := False;
end;

拦截消息
unit Unit1;
interface
uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,MaxDirFile;
type
TForm1 = class(TForm)
procedure FormCreate(Sender: TObject);
private
{ Private declarations }
protected
procedure WL(var Message:TWMLBUTTONDOWN);message WM_LBUTTONDOWN;
procedure WDL(var Message:TWMLBUTTONDBLCLK);message WM_LBUTTONDBLCLK;
public
{ Public declarations }
end;

var
Form1: TForm1;
implementation
{$R *.DFM}
procedure TForm1.FormCreate(Sender: TObject);
begin
MaxDirFile.GetAppDir
end;

procedure TForm1.WDL(var Message: TWMLBUTTONDBLCLK);
begin
Showmessage(‘ddd‘);
Message.Result:=0;
end;

procedure TForm1.WL(var Message: TWMLBUTTONDOWN);
Var
Pos:Integer;
Key:integer;
begin
Pos:=(Message.YPos shl 16)+Message.XPos;
Key:=Message.Keys;
SendMessage(handle,WM_LBUTTONDBLCLK,Key,Pos);
Message.Result:=-1;
end;

end.