Duplicates within expanded rows specific to each acct #

Hi, I have a pivot table of acct #s with data listed for each acct #.

I need to find duplicates, not across the entire pivot, but just duplicates (if any) within each acct # listed.

To see the data for each acct #, you have to expand the (+) the line item within the pivot.  How do I find the duplicates, specific to each acct # for a pivot of roughly 150k acct #s? (not duplicates across the entire pivot).  Thank you so much in advance for any feedback!!