JD,
Assumed the row1 has the headings.
select A2:A21 (A2 should be the active cell)
FormatConditional Formatting
in the Conditional Formatting dialog box
change the "cell value is" to "formula is"
and type the following formula
=COUNTIF($A$2:$A2,$A2)1
click Format button and select the colour from the patterns page
click OK, OK
Cecil

"JD" wrote in message
...
If I type the same number in the same colum say ( D )
is there a way to flag ,make a sound,and or change color
in that cell that i have entered a duplicate number