I am trying to identify duplicates between two columns. Column A has a
number of customers. Column B has their purchases. I want to identify any
duplicate records in column B for each group of customers in column A. Any
ideas?

See example below. In this example, I would like to highlight/identify Eggs
for Joe (as Eggs are the duplicate in Column B); Cereal and Bread for Susan;
Pete is fine (no duplicates).

I would then need to create a report that would give me Joe and only Eggs
(once) and Apples; Susan Bread (once) and Cereal (once); etc.

Column A Column B
Joe Eggs
Joe Eggs
Joe Apples
Susan Cereal
Susan Bread
Susan Cereal
Susan Bread
Pete Milk
Pete Eggs