Flag object to differentiate the Cust IDs coming from 2 different data providers

I need help with.

I've 2 data providers, the Cust IDs in each are as following

All Cust -- Safety Cust
C01 -- C01
C02 -- C02
C03 -- C03
C04
C05
C06

But, these two are coming from different tables in the database, one is the permanent Cust table and the Other is a User Upload Cust table.

Now in the report, I merged on Cust ID........I need to create a Flag for Satefy Cust (C01, C02, C03) and the rest will be All Others.

I need this flag to get different measures like.....Sales Amt for Safety Cust , Sales Amt for All Other Cust etc