主程序如何知道系统单击鼠标事件？（下面程序如何修改）

library GMousehook;uses
  SysUtils,wintypes,winprocs,messages,windows, Dialogs, mousehookdemou,
  Classes;
var
  ishooked:boolean;
  hookhandle:hhook;
  desktopwin:hwnd;
  OldProc:FARPROC;function hookproc(code:integer;wparam:wparam;lparam:lparam):lresult;stdcall;
var
WinStr:HWND;
var form1:tform1;
begin
  if wparam=WM_LBUTTONDBLCLK then
  begin
  {messagebeep(mb_iconasterisk);
  WinStr:=FindWindow(nil,'form1');
  OldProc:=FARPROC(GetWindowLong(WinStr,GWL_WNDPROC));
   //SetWindowLong(WinStr,GWL_WNDPROC,Longint(@WinProc));
   mousehookdemou.s:='asdf'; }
   form1:=tform1.Create(nil);
   form1.Label1.Caption:='123';
   showmessage('鼠标事件');
  end;
  result:=callnexthookex(hookhandle,code,wparam,lparam);
end;function sethook:boolean;stdcall;
begin
result:=false;
if ishooked then
exit;
//desktopwin:=getdesktopwindow;
hookhandle:=setwindowshookex(wh_mouse,hookproc,hinstance,0);
ishooked:=true;
result:=hookhandle<>0;
end;Function WinProc(Hwnd,Msg,wParam,lParam:longint):LRESULT; stdcall;
begin
{在这做出对消息的处理  case Msg of
    WM_ACTIVATEAPP:exit;
    WM_ACTIVATE:exit;
    WM_KILLFOCUS:exit;
    WM_SETFOCUS:exit;
  end;
上面这些消息是窗口失去焦点和获得焦点的屏蔽
}
//将窗口消息传递给Windows处理
Result:=CallWindowProc(OldProc,Hwnd,Msg,wParam,lParam);
end;function removehook:boolean;stdcall;
begin
result:=false;
if (not ishooked) and (hookhandle<>0) then
result:=unhookwindowshookex(hookhandle);
ishooked:=false;
end;
exports
  sethook name 'sethook',
  removehook name 'removehook',
  hookproc name 'hookproc';{$R *.res}
begin
  ishooked:=false;
end.
主程序：
unit mousehookdemou;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    Label1: TLabel;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
  private
    { Private declarations }
  public    { Public declarations }
  end;
  function sethook:boolean;stdcall;
  function removehook:boolean;stdcall;
var
  Form1: TForm1;
  s:string;
implementation
   function sethook;external 'gmousehook.dll' name 'sethook';
   function removehook;external 'gmousehook.dll' name 'removehook';
   
{$R *.dfm}procedure TForm1.Button1Click(Sender: TObject);
begin
 if sethook then
 showmessage('global mouse hook set, click on desktop ')
 else
 showmessage('global mouse hook not set');
 
end;procedure TForm1.Button2Click(Sender: TObject);
begin
if removehook then
 showmessage('global mouse hook removed,click on desktop')
 else
 showmessage('global mouse hook not removed');
end;procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
showmessage(s);
end;
end.
程序如何修改，请指教？