Hi, I found this post very interesting and am very impressed with the
formulas provided, however I would like to ask for something extra
which I don't know if is actually possible (without VBA).

From the above post..

(b) all the unique combinations of surname and first name (in the
above example it's 4, . . .)

Gets more complicated, but still possible with a single ARRAY formula
using only built-in functions.

=SUM(1/MMULT(--(A1:A6&";"&B1:B6=TRANSPOSE(A1:A6&";"&B1:B6)), ROW(A1:A6)^0))

I would like a modification to so that only the unique combinations of
surname and first name where first name = John are returned (thus 2 in
the example).

Any help would be appraciated as I'm stuck :-)

Thanks.