You can use conditional formatting for this. Select the range where your
numbers are, say A1:A1500, then go to formatconditional formatting. Formula
is =COUNTIF($A$1:$A$1500,A1)1

then set color to red or whatever will tell you it's a duplicate.



"Iboa" wrote in message
...
I work with excel all day long in my job. I use a hand scanner(SYMBOL
LS4000i) to scan bar codes for the product we sell. Sometimes I scan the
same s/n: by accident. I will like to now if there is anyway the computer
will tell me right a way when I scan the same item twice.

Thanks

Iboa