Is there a calculation that would let me create 12 fields that I could use as headers in a layout where the first field would display the prior completed month name and then the remaining 11 fields the month names before that?

So as we are in april:

Field 1 | Field 2 | Field 3 | Field 4 | Field 5 etc...

Apr | Mar | Feb | Jan | Dec

Use a field with 12 repetitions and a script.

If you need different formatting, use differently specified repetitions of the same field

(e.g. [1] on its own, and [2] to [12] grouped together).

MonthFill.fp7.zip

How about something a bit more simple - and a bit more flexible?

MonthLabels.fp7.zip

Thanks to you both! I learned something with both techniques