Assume names of the people to whom a letter was sent are in column
A:A.

Assume the entire list of names is in column B:B.

Then using a formula like =MATCH(B1,$A$1:A$100,0) in column C:C and
filled down to the end of column B will tell you which names in column
B appear in column A. Those names that are in both columns will
return a number; those names that are only in column B (i.e., have not
been sent a letter) will return a #N/A error.

Dave

On Dec 18, 9:36 am, PayPaul wrote:
I have two mailing lists on two separate worksheets. On one worksheet I
mostly entries for contacts that were sent a letter. On the other I have some
names of people associated with some clients that were not sent the mailing.
It's a huge spreadsheet. How do I separate out the names and clients who were
sent the mailing from those that weren't on the second worksheet?