help needed - discount formula

For another array of products we have 3 productoptions - PriceIncrement of '0' '-9' '15'. Instead of only discounting where PriceIncrement is '0', I would like to be able to discount these other options similarly (same idea - Buy One/Get One).

I imagine I could create two more columns, name them possibly DiscountableA & DiscountableB, and apply your previous instructions - create 2 new calculation tabs entries - add 2 'OR' conditions to the trigger - amend the calculation to also include DiscountableA and DiscountableB (which I would ask for help with the correct syntax) ... but is there a simpler way to program the cart to recognize each of the three options separately and apply the correct amount of discount (which was 8 in the previous example, but would in effect be dynamic - 50% given the specific productoption price selected)?

Thanks for any help ...