I need to make a discount like this: if I have one Item in order - no discount, if I have 2 items - 1-st no discount, second - 10%, 3 itrms - 1 - 0%, 2 - 10%, 3 - 20%. If I have more then 3 Items - 1 - 0%, 2- 10%, 3 - 20%, 4 and others - 30%. Where are no standart trmplates to do this, but I fount ItemTieredPriceCalculator, which is suitable for the task. But it doesn't extends ItemDiscountCalculator, so I cani't use it in Item discount template. Is where any way to use it in promotions?