ARRAYFORMULA Using Row Above - Google Spreadsheet

Question

I would like to create a column that contains a running decrementing tally, but is decremented by an amount from a different column on the same spreadsheet. Also, I would like to be able to add rows, without modifying this function. (i.e. such that this function will "Autofill" automatically when I insert new rows)

It seems like the ARRAYFORMULA will do this, but every time I've tried, I get a circular reference error. I have an example spreadsheet below with this error, can anyone correct my formula?

https://docs.google.com/spreadsheet/ccc?key=0AqcS_eDL_8umdEtLQ2s5Y1VYNk1wZUZrb25PajhfTkE&usp=sharing

Answer 1

You get a circular reference because you have

=ARRAYFORMULA(C2:C - A3:A)

in column C. This is circular reference because column C references itself (C2:C) in the formula.

What you need is something like the following in column C

=ARRAYFORMULA(B2:C - A3:A)