Any way to enforce incremental numbering in columns?

[MrSteve]

Four things:

The cell L1 is formatted as text, so no formula will work there. Change it to General, and recalculate the formula (seleect L1, F2, Enter)

Because the helper cell is L1, you have to change the reference in the DV to that cell, so the $C$1 becomes $L$1.

In my narrative I said starting at A1. You are starting at A2, so the firts cell in the DV formula has to chnage from ($A2 to $A3.

I said an Allow type of List, you have left it as Custom.

DOH!

Thanks again for your help. It is much appreciated.