That sorta' works, Max. Almost. Thanks, but...

About 80% of the 140,000 records have the ID of 1557.
Starting at #24,643, ALL of the records after that have that ID #1557.
Records from #24,643 to 91,884 all indicate "0" in Column C, as they
should.

For some reason,... starting at record # 91,885,
some of the records show "0" and some show "1".

I can see no pattern as to why this happened.

Have ya' got an explanation?

Thanks.

Mark246



On Feb 25, 5:20 am, "Max" wrote:
Is there a way to select only the cells / rows in Column B that match
the ID numbers in Column A?

One quick & easy way is to use autofilter on a helper col
Assuming source data in cols A & B, data from row2 down
Put in C2:
=IF(B2="","",--ISNUMBER(MATCH(B2,A:A,0)))
Copy C2 down to the last row of data in col B