Install A hook to All threads

i want to install the hook all the threads not only the current thread.

how can i do that?

i would like to monitor all mouse messages.
i made a program seen below.
it uses Wh_Mouse hook but doesnot work when the mouse cursor is outside of my application. While the mouse cursor is somewhere on my form, it displays mouse x,y point.
i guess i forget something.

the code is below :

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Label1: TLabel;
    Label2: TLabel;
    procedure FormCreate(Sender: TObject);
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
  private
   FHookHndl : THandle;
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

type
  MouseProc = function (nCode : Integer;
                    WParam: WPARAM;
                    LParam: LPARAM): UINT; stdcall;

{$R *.DFM}

var
   proc:MouseProc;

function MyMouseProc(nCode : Integer; WParam: WPARAM; LParam: LPARAM): UINT; stdcall;

function GetXY : TPoint;
begin
 Result := PMouseHookStruct(LParam)^.pt;
end;

begin

 if ncode<0 then
    begin
     Result := CallNextHookEx(Form1.FHookHndl, nCode, WParam, LParam);
     exit;
    end;

 case WParam of
    WM_MOUSEMOVE:
       begin
         Form1.Label1.Caption := IntToStr(GetXY.X)+'/'+IntToStr(GetXY.y);
       end;
 end;

 Result := CallNextHookEx(Form1.FHookHndl, nCode, WParam, LParam);
end;


procedure TForm1.FormCreate(Sender: TObject);
begin
 Proc:=MyMouseProc;
 FHookHndl := SetWindowsHookEx(WH_MOUSE, @Proc, 0, GetCurrentThreadID);
 if FHookHndl>0 then
    MessageDlg('Hooked', mtInformation, [mbOK], 0);
end;

procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
 if UnhookWindowsHookEx(FHookHndl) then
    MessageDlg('UnHooked', mtInformation, [mbOK], 0);
end;

end.