I use a product attribute called "carton" which describes in how many carton a product is packed. I want to add a cart-rule which counts the amount of all cartons in the cart (accordingly the amount entered for each product in carton product-attribute).
According the total amount of cartons i want to offer special discount.
The function is similar to the weight function which also make a sum of all weight in the cart.
Your help would be really appreciated! Thank you