Paypal Discount When purchasing two + items (not two instances of same object)

Paypal has listed out methods for discounts such as :

discount_amount

Optional Discount amount associated with an item. It must be less than the selling price of the item. If you specify discount_amount and discount_amount2 is not defined, then this flat amount is applied regardless of the quantity of items purchased. Valid only for Buy Now and Add开发者_如何学C to Cart buttons.

discount_amount2

Optional Discount amount associated with each additional quantity of the item. It must be equal to or less than the selling price of the item. A discount_amount must also be specified as greater than or equal to 0 for discount_amount2 to take effect. Valid only for Buy Now and Add to Cart buttons.

I understand that you can have a discount associated with the amount of the same object inside of the cart. I'm wondering if anyone knows a way or method to allow a discount to show up if you say add 3 items or 5 items. Basically the situation is users have the option of signing up for either 1-4 courses. If a user signs up for 1 normal price(lets say 30) occurs. If a second is added they would receive a 10 dollar discount on the tuition(50). Than if a third is added it would show up as the regular method (resulting in 90) However if a fourth is added it would be a charge of 3 courses plus 50. (95). Is there any solution to presenting this to paypal to update based on amount of items (each being different items[different course dates and names]) included in your cart?

If it's for the whole cart and not just the item use discount_amount_cart

Remember discount_amount_1 has to be less in value than amount_1