Custom calculated value

Sometimes you need to show not just attribute, but sum of attributes (like total length or new price)

You can customize Product Labels extension to meet your needs, It's quite easy.

Please open file app\code\local\Amasty\Label\Model\Label.php, find lines

case 'PRICE':
  $value = strip_tags($store->convertPrice($this->_info['price'], true));
break;

and add lines like
case 'PRICE':
  $value = strip_tags($store->convertPrice($this->_info['price'], true));
break;
case 'MY_NEW_VALUE':
  $price2 = $p->getData('designtool_price');
  $price3 = $this->_info['price'];
  $value = strip_tags($store->convertPrice( $price2 + $price3, true));
break;

Then use {MY_NEW_VALUE} in admin