form_validate_quantity = function() {
  if ($('quantity').value < 1) {
    $('giftcard-error-message').update("Quantity must be 1 or greater");
    $('giftcard-error-message').show();
  }
  else {
    $('giftcard-error-message').hide();
  }
}

form_validate_amount = function(minimum_value, maximum_value) {
  if ($('amount').value < minimum_value || $('amount').value > maximum_value) {
    $('giftcard-error-message').update("Amount must be between " + minimum_value + " and " + maximum_value);
    $('giftcard-error-message').show();
  }
  else {
    $('giftcard-error-message').hide();
  }
}