glenlee wrote:
In the case where the start number in col A is -0- your formulas
below return a result of 100% which is mathematically incorrect.

As I said, the choice of 100% is arbitrary.

Thus I vote for this formula:
=IF(A1=0,"NA",IF(A10,(B1-A1)/A1,(B1-A1)/(-1*A1)))

"To each his own". I prefer homogeneous results -- always
numeric, in this case. It makes it easier to write dependent
formulas. A wise choice for the delta from zero would be a
large percentage for your application, but not so large that
it would skew all other computation. IMHO, 100% usually
fits the bill. But those who struggle with reading, I repeat:
it is arbitrary, it depends on your application, and "to each
his own".

And for Pete's sake, "-A1" is the same as "-1*A1" and
"-(B1-A1)/A1" is equivalent and easier to write.