Hi,

I set up an auto sequence number (column B) based on the date entries in column A (see example below) using the following formula:
=IF(ISBLANK(A45),"","PERM"&"_"&TEXT(A45,"YYYYMMDD")&"_"&TEXT(COUNTIF($A$5:A45,A45),"0"))

It all works fine, until I start to re-sort the data entries by the various columns. Then, an entry that had previously assigned sequence number PERM_YYYYMMDD_3 maybe suddenly become PERM_YYYYMMDD_1.

Is there a formula that will allow me to assign a permanent unique sequential number independent of the sort order?

Column A Column B
12/02/2014 PERM_20140212_1
12/02/2014 PERM_20140212_2
12/02/2014 PERM_20140212_3

Thanks so much for your help!
Barbara