dynamic range (based on current date/month)

users
#1

Better, but no cigar. You twice above say to the *current month* (change to August on 1 August; "current month") and twice suggest the previous month (MONTH(TODAY())-1; "prior month"). The formula will differ depending on which you require, of course.

Let's suppose you have the months in columns from B to M. Then try:
=SUM(Bn:OFFSET(Bn,0,MONTH(TODAY())-1))

The OFFSET() function here takes a reference to Bn - the January cell - and offsets it by MONTH(TODAY))-1 cells to the right. So today, in July, this is six cells to the right, or Hn. The SUM() function sums from Bn to Hn, which is what you require for July.

If you want the sum to the previous month, you could start with:
=SUM(Bn:OFFSET(Bn,0,MONTH(TODAY())-2))
- but this would not work for January, where you actually need to sum nothing. You probably need to handle that as a special case by including an IF() in your expression:
=IF(MONTH(TODAY())=1,0,SUM(Bn:OFFSET(Bn,0,MONTH(TODAY())-2)))

I trust this helps.

Brian Barker