Hi Peter

You can use conditional formatting to identify dates in common between two
columns. Let's assume that your dates are in columns A and C. Select column
A and pull-down:

Format Conditional formatting select {formula is} and enter

=ISERROR(MATCH(A1,$C$1:$C$10,0)) and pick a distictive format. The
distictive cells will be not-matches. You can expand the $C$10 to whatever
you column size is.

--
Gary's Student


"Peter" wrote:

excel 2003 - office professional.
I have data for water temperature from two reservoirs taken over 5 years. I
want to match the water temperatures from the two reservoirs only for samples
taken on the same day as not all samples were taken at the same time. I
therefore have four columns: 1) date of sample for reservoir 1; 2) nitrate
reservoir 1; 3) date of sample reservoir 2; 4) nitrate reservoir 2.
There are uneven sample numbers for each reservoir where there was some data
missing from one of the reservoirs.
Many thanks