I have the PHP version up and running and am in process of setting up the shop. I am trying to find how to add an option that allows a customer to purchase a variable amount - so the OPtion, such as SELECT, needs to add a percentage of the fixed fee. For example, if I am selling rope cut to whatever length the customer wants, then I can cut and supply whatever length the customer wants. I can use SELECT to add a one off cutting fee, but how to I calculate the amount if the customer wants say just 15 meters.
Thanks in advance