My worksheet has blocks of 6 rows for each item I'm reporting on. I want to
apply a formula to the last row in each section, using data from the previous
column and the other cells in the same column, i.e

b6 = sum(a6-b1-b2-b3-b4+b5)
c6 = sum(b6-c1-c2-c3-c4+c5) etc.

I think I can get to each 6th row, by

if(mod(row(a1:a240) - 1),6) = 0, but not sure how to apply the formula

Thanks for any suggestions