incremental charge
Hi Erick,
Are your sizes stored in a database table?
In my experience, in order to acheive what you describe, you'd need to add an additional field to your 'Sizes' database table which stores an incremental value, $3 in your case, for each size that you need to charge an additional fee for.
You then need to store that incremental value in your cart, when the customer is adding items to basket, and add/apply that incremental value to the 'Price' value once it's in the basket.
Hope that gives you some ideas.
Nath.