Mike,

If your 12 digit strings are in column A, starting in Row 2, then in cell B2 use the array formula
(entered with Ctrl-Shift-Enter)

=IF(COUNTIF($A$1:A2,A2)1,VLOOKUP(A2,$A$1:$B2,2,FA LSE),TEXT(MAX(VALUE($B$1:B1))+1,"0000"))

and copy down to match your list in column A. It will work, possibly slowly depending on how big
your list is...

HTH,
Bernie
MS Excel MVP


"mikep" wrote in message
...
I'm trying to convert 12 digit strings to individually unique 4 digit strings
for product coding. Any ideas?