We are a non-profit who has multiple trips each year to developing countries to do medical and construction work (Rotary). Our volunteers pay to go on these trips. I set up each trip as a Campaign, each person on the trip is a Campaign Member (who is also a Contact record). I want to track payments made by each Campaign Member (there are installments of 3 to 4 payments).

I think I want to set up a master-child relationship between a custom object (e.g. Payments) and the Campaign Member. That way, I could roll-up the total payments to each member. Addtionally, since people (e.g. Contacts) travel on multiple trips, I could see the payment information at the Campaign Member level so each Contact would have multiple Campaigns and multiple Payments.

However, when I try to create a master-detail relationship between Payments and Campaign Member, the option to select Campaign Member as the master is not shown in the list of available objects. I could do Contact or Campaign, but I think I want the Campaign Member. Eventually I will have automated code that will create the Payments records and associate them with each Campaign Member when each Campaign Member pays on PayPal.

Ideas? Thanks so much!