Accumulating promotion
My company has a promotion which lasts for 30 days. If the customer purchases 300 units of item A , they will receive 60 free units of item A. The 300 units can be purchased in one order, or the customer can accumalate the quantity of 300 over separate smaller orders, providing the 300 units has been reached within the 30 day promotion period.
The company also wants to know how much the customer spends in this 30 day period. I have set up a period 1 item amount = 30 day.
Please can I be advised about how to set up this promotion.