Hi,
I have a excel like this:

A B C D

1 MAKE BEFORE AFTER

2 Audi 154 340


3 Toyota 165 350

I want D to be the percentage difference between column B and C and used the following formula in D2 =SUM(100/(B2/(C2-B2))
That gives me the right answer in D2 but for D3 I have to change the formula to read 3 instead of 2 and to do this for many rows is not very efficient. Is there a formula I can use to make column D read for the corresponding rows in colum B and C all the way down.
Sorry if this is a really dumb simple question but Im pretty new at this and not real good at maths
thanks.