First Create your Custom Order Content type and add your custom properties

[ContentType(GUID = "9ef12797-913d-46c4-87a7-ceecdd62081c")]
 public class MyOrderDiscountPromotion : OrderPromotion
 {
 /// <summary>
 /// The percent of amount off the order.
 /// </summary>
 public virtual decimal Discount { get; set; }
}

Then create a processor which is called by the promotion engine to apply the promotion

public class MyOrderDiscountPromotionProcessor : OrderPromotionProcessorBase<MyOrderDiscountPromotion>
{
 public override RewardDescription Evaluate(MyOrderDiscountPromotion promotionData, PromotionProcessorContext context)
 {
 throw new NotImplementedException();
 }

 protected override bool CanBeFulfilled(MyOrderDiscountPromotion promotionData, PromotionProcessorContext context)
 {
 throw new NotImplementedException();
 }

 protected override PromotionItems GetPromotionItems(MyOrderDiscountPromotion promotionData)
 {
 throw new NotImplementedException();
 }
}

The PromotionProcessorContext contains all information from the “context” we need to evaluate the promotion.

Hope this is enough to get you started.

Thanks Johnny,