Thread: Tally serial number for excel

Your example is not all that clear, perhaps you're saying you want to use Conditional Formatting against the values in A to highlight any serial numbers that appear more than once (once they have been collated from the various source files), if so then:

-- highlight A2:A100 (change according to likely quantity of data) being sure to select A2 first
-- Format -> Conditional Formatting
-- use a FormulaIs approach
-- set Formula to be: =COUNTIF($A:$A,$A2)>1
-- set Format to be applied to duplicates accordingly

Now if a number should appear more than once in your A2:A100 range all instances of said number will be formatted per your set format such that you can easily identify them.