cakePHP: how set error validation to input field manually in controller

I want set error validation to input field manually in controller example:

  if ($remainTime < 30) {
      ..... set error validation in here (error: limitTime ), ( error is not in model )
  }

other question: i want to ask : bindModel ( in this case , I use bindModel in Behaviors ) 'll cause loss of relationship with other model but is bindModel cause loss of $var validate,too ?