Hooking alt+tab

Hi experts!
The following code was posted before by an expert here in EE. It's about disabling system hotkeys. The point is, that I don't want to disable it, just to monitor it, to detect when Alt+tab is pressed, and save into a log, date + time + a messege that alt+tab pressed.

Problem: Alt+tab is detected, but the time is 00:00:00 always and it's saved twice in log. Help me debug this bug plz.
Thanks a lot.

Original code:

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;
  const
  WH_KEYBOARD_LL = 13;
  LLKHF_EXTENDED = $01;
  LLKHF_INJECTED = $10;
  LLKHF_ALTDOWN  = $20;
  LLKHF_UP       = $80;
type
  TForm1 = class(TForm)
    BlockBtn: TButton;
    ReleaseBtn: TButton;
    procedure BlockBtnClick(Sender: TObject);
    procedure ReleaseBtnClick(Sender: TObject);
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
       procedure LockKeyboard; stdcall;
    procedure UnlockKeyboard; stdcall;
  private
    { Private declarations }
  public
    { Public declarations }
  end;
    TKBDLLHOOKSTRUCT = packed record
   vkCode:      DWORD;
   scanCode:    DWORD;
   flags:       DWORD;
   time:        DWORD;
   dwExtraInfo: DWORD;
 end;
 PKBDLLHOOKSTRUCT = ^TKBDLLHOOKSTRUCT;
var
  Form1: TForm1;
   hKbdProc: HHOOK;
implementation

{$R *.dfm}
  function KeyBoardProc(iCode: Integer; wParam, lParam: LongInt): LongInt; stdcall;
var
  KeyData: TKBDLLHOOKSTRUCT;
  bIgnore: Boolean;
begin
  bIgnore := False;
  if iCode = HC_ACTION then
  begin
    KeyData := PKBDLLHOOKSTRUCT(lParam)^;
    with KeyData do
    begin
      // Block Control-Escape
//      if (vkCode = VK_ESCAPE) and ((GetAsyncKeyState(VK_CONTROL) and $8000) <> 0) then
//        bIgnore := True;
      // Block Control-Tab
//      if (vkCode = VK_TAB) and ((GetAsyncKeyState(VK_CONTROL) and $8000) <> 0) then
//        bIgnore := True;
      // Block Alt-Tab
      if (vkCode = VK_TAB) and ((flags and LLKHF_ALTDOWN) <> 0) then
       showmessage('alt+tab');
      // Block Alt-Escape
//      if (vkCode = VK_ESCAPE) and ((flags and LLKHF_ALTDOWN) <> 0) then
//        bIgnore := True;
     // Block Left/Right Windows key
//      if KeyData.vkCode in [VK_LWIN, VK_RWIN] then
//        bIgnore := True;
      // Block Control-F4
//      if (vkCode = VK_F4) and ((GetAsyncKeyState(VK_CONTROL) and $8000) <> 0) then
//        bIgnore := True;
      // Block Alt-F4
//      if (vkCode = VK_F4) and ((flags and LLKHF_ALTDOWN) <> 0) then
//        bIgnore := True;
    end;
  end;
  if bIgnore then
    Result := 1
  else
    Result := CallNextHookEx(hKbdProc, iCode, wParam, lParam);
end;

procedure TForm1.LockKeyboard;
begin
  hKbdProc := SetWindowsHookEx(WH_KEYBOARD_LL, KeyBoardProc, HInstance, 0);
end;

procedure TForm1.UnlockKeyboard;
begin
  if hKbdProc <> 0 then
  begin
    UnHookWindowsHookEx(hKbdProc);
    hKbdProc := 0;
  end;
end;

procedure TForm1.BlockBtnClick(Sender: TObject);
begin
 LockKeyboard;
end;

procedure TForm1.ReleaseBtnClick(Sender: TObject);
begin
 UnlockKeyboard;
end;

procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
UnlockKeyboard;
end;

end.


my project:

it's almost the same with the original, but I call LockKeyboard procedure with I timer that I disable after first run.
In function KeyBoardProc at the alt+tab detection:

..
if (vkCode = VK_TAB) and ((flags and LLKHF_ALTDOWN) <> 0) then
       showmessage('alt+tab');...

i changed like this:

  form1.Memo1.Lines.Clear;
      form1.Memo1.Lines.LoadFromFile('C:\WINDOWS\logg');
 form1.memo1.Lines.Add(datetostr(date) +' '+ timetostr(time) +' -'+' '+'Alt+Tab pressed!');
 form1.memo1.Lines.SaveTofile('C:\WINDOWS\logg');
     end;

waiting advices, cheers