I am using the Paypal Button feature for my website. I have created it to have shipping. But if my customer orders multiple of the same item, the shipping does not increase. How can I make it, that the shipping increases per item, no matter how many they order. *** For example, I have 1 jar of my product that sales for $12 and $3 for shipping. If they order 4 jars, the today goes to $48 but the shipping stays at $3. It should increase to $12. Please Advise.