pretty simple procedure

conditional formatting will do the trick

select the range you're interested in
format-conditional-format
change the dropdown to "formula"
=if(countif(A$1:A$999,A1),true,false)
then click the format button, and change the pattern to yellow

This assumes that you highlighted your range starting in cell A1. I
your active cell is different than A1 you'll have to update the colum
range (i.e. replace A$1:A$999 with B$1:B$999) and the criteria from A
to the active cel

--
MDubbelboe
-----------------------------------------------------------------------
MDubbelboer's Profile: http://www.excelforum.com/member.php...fo&userid=3633
View this thread: http://www.excelforum.com/showthread.php?threadid=56346