Highlighting duplicates within subtotals groups only (not entire sheet or column)

Title explains it: Wondering if there's a way to search only information within a subtotal grouping in order to highlight duplicate values within that subtotal.

Added complication, cells are subtotaled by Column A, I want to search Column B for duplicate values within the subtotal. There will be many duplicates throughout Column B in general, but I want to ID if there are duplicates within the subtotal groups ONLY.

Is this possible? Via what route? Game to try and figure out the actual method specifics myself, but do need a point in the right direction or to know if this is even possible.

TIA!

Absolutely - please see attached.

Basically looking to subtotal / group by Dance Name (Column A), and then identify / highlight orders that are for the same person in Dancer First Name (Column B). For example, within the Dance/Column A "Brown", Karine Jean-Pierre appears twice. I'd need to catch that.

The actual excel will b a few hundred entries.

If there's a better way to do this, I'm I'll ears.

The Excel will be used in a mail merge after this to make labels so this is a consideration as well.

Thanks!