Hi @LBrown3,
Yes, it is possible via workflow and a custom property. The below steps will help you;
1. Create a Contact Custom Property and name it “Interest”
2. Create a workflow to set the “Interest” value as per the interaction of the user with emails
3. Now on the bases of the “Interest” value we can add or remove any user from a particular emailing list.
Please reply below if you face any problems while implementing the above steps.
Thanks 