I have an order form that has up to six areas to select and add product to a gift pack. What I need is to have the total qty of all items placed in the gift pack to equal 6, 12, 18, 24, 30 or 36. Only multiples of 6 with 6 being the minimum amount and 36 being the maximum.
I don't know how to do this. Any pointers would be great.