This is an extract of my source data with thousands of records. I want
to know the no. of cutomers (unique count) associated with each
product without deleting any records from the source file. Is there
any formula/function which I can use? E.g For product 2, there are 4
unique customers while product 4 has only 1 unique customers?

Customer 1 Product 1
Customer 2 Product 2
Customer 7 Product 2
Customer 5 Product 2
Customer 3 Product 2
Customer 2 Product 2
Customer 2 Product 3
Customer 3 Product 4
Customer 4 Product 4
Customer 4 Product 4