Malletin

I post this question on behalf of a friend: Is there anyway to get the promo code for the presale of tickets for the Chicago performances of Mama Mia? We live in Cedar Lake Indiana and only get out to woodfield at the holidays, but want to see Mama Mia, and saw a presale if you came to the guest services for ticketmaster at woodfield mall. Is it possible to find out that promo code, in order to purchase tickets? Thank you.