My client wants the user to only be able to only order up to 12 units of one product. I will leave a disclaimer on the site informing the user to call in orders of 13 pieces or more if they are the same size and formula.
The user can order up to 12 of each different product. I know it sounds weird (i agree), but that is what my client wants. They primarily have clients that are big manufacturing facilities that would call in a bulk order. The website is set up to cater more to the "do-it-yourself" customer, which would normally order only up to 1 case of 12.
The case price only applies if the products are the same size cartridge. They may mix and match within a size to get to 12 items if they wish.
To be clear: a maximum of 12 can be ordered of each product. The user may order up to 12 of every product on the site. 12 is the cut off for any one glue that is the same size and part number.