Membership Benefits and Incidents for Certain Levels Only

Jenny Smith 3

We are wanting to do a Cyber Monday Deal that gives all membership purchases an Unnamed Adult Membership add-on. How can we restrict the code for online only and can only be applied if they add the Unnamed Adult option. Currently using a code would apply the discount amount to any membership they purchase, reducing the cost instead of getting the add-on. I think this might be better suited as a benefit but not finding enough information to say for sure.