鼠标定位(35分)

在一个窗体显示后，如何使鼠标只能在这个窗体中移动，而不能移到此窗体这外的
某个地方，当窗本关闭后鼠标自由移动
本人急用，请高手给出源代码！！急！急！急！（35分献上）

var rct:trect;
rct:=self.ClientRect ;
clipcursor(@rct);

unit Unit1;
interface
uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,stdctrls;
type
TForm1 = class(TForm)
Button1: TButton;
Button2: TButton;
procedure Button1Click(Sender: TObject);
procedure Button2Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;
implementation
{$R *.DFM}
procedure TForm1.Button1Click(Sender: TObject);
var rtbutton2:trect;
begin
rtbutton2:=button2.BoundsRect;
mapwindowpoints(handle,0,rtbutton2,2);
clipcursor(@rtbutton2);
end;

procedure TForm1.Button2Click(Sender: TObject);
var
rtscreen:trect;
begin
rtscreen:=rect(0,0,screen.width,screen.height);
clipcursor(@rtscreen);
end;

end.

Thank you!!!!!!!!!!