ReadDirectoryChangesW 无法监视文件变化

[cyradg2008]

代码如下：

procedure TForm1.ToolButton4Click(Sender: TObject);
var
  FD:Thandle;
  BytesToWrite: DWORD;
  Buffer:array [0..1023] of byte;
  overlapped:TOverlapped;
begin
  FillChar(Buffer,sizeof(Buffer),0);
  FD := CreateFile(PChar('\\?\D:\PC游戏\Diablo\Save\'), GENERIC_READ or GENERIC_WRITE or FILE_LIST_DIRECTORY , FILE_SHARE_READ or FILE_SHARE_WRITE or FILE_SHARE_DELETE, nil,
    OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS or FILE_FLAG_OVERLAPPED, 0);
  FillChar(overlapped,sizeof(TOverlapped),0);
  Overlapped.hEvent := CreateEvent(Nil, True, True, Nil);
  BytesToWrite := SizeOf(TFileChangeInfo);
  ReSetEvent(Overlapped.hEvent);
  if ReadDirectoryChangesW(FD, @Buffer, SizeOf(Buffer), false,
    FILE_NOTIFY_CHANGE_FILE_NAME or FILE_NOTIFY_CHANGE_DIR_NAME or
      FILE_NOTIFY_CHANGE_ATTRIBUTES or FILE_NOTIFY_CHANGE_SIZE or
      FILE_NOTIFY_CHANGE_LAST_WRITE or FILE_NOTIFY_CHANGE_LAST_ACCESS or
            FILE_NOTIFY_CHANGE_CREATION or FILE_NOTIFY_CHANGE_SECURITY,
      @BytesToWrite, @overlapped, nil) then
  begin
    Caption :=Inttostr(GetLastError);
    WaitForSingleObject(Overlapped.hEvent, INFINITE); // 等待事件发生
  end
  else Caption :=Inttostr(GetLastError);
  CloseHandle(FD);
  CloseHandle(Overlapped.hEvent);
end;

当监视目录下某个文件内容变化时，WaitForSingleObject(Overlapped.hEvent, INFINITE);无法等待到hEvent事件，也就是hEvent一直阻塞，主程序一直阻塞，请问ReadDirectoryChangesW如何监控文件变化？

[日立奔腾浪潮微软松下联想]

最后一个参数是回调函数~~~