Discount Code for Multiple Event Tickets

We're using Ticket Pro to sell tickets for our annual recitals, but we have 2 shows (1 on Saturday and 1 on Sunday). Since the recitals are on different days we needed to create 2 different events. We have some dancers who are in only one show, but some dancers are in both. We'd like to offer a discount for parents who have dancers in both shows and would like to purchase tickets to both shows, but currently there's no way to ensure those receiving the discount are in fact purchasing tickets from both shows. I'd like to suggest adding this option to your promo code feature.