Ok, I think my example may have been a bit too simplistic. Let's try
one a little more complex.

Row 1: 18 18
Row 2: 14 32
Row 3: 10 42
Row 4: 3 45
Row 5: 20 65
Row 6: 5 70

So formula in B1 is =SUM($A$1:A1). Formula in B2 is.....
=SUM($B$1:B1)?