Sales from Existing Customers purchasing first-time products + Sales from Existing Customers purchas

Current Year Sales = Sales from New Customers + Sales from Existing Customers purchasing first-time products + Sales from Existing Customers purchasing repeat products

Standard Data Model 

Fact: Sales

DImension: Products, Customers, Dates

1. Create a Calculated Column "New/Existing" in Customers table. "New" if it has purchased this year but not last year. "Existing" if it has purchased both years. THis is pretty straight forward. 

2. How do I go about creating a measure/column/any-solution that is "First-time ProductSales" and "Repeat Product Sales"