Hi,

Not exactly sure what your looking for but maybe:

=IF(A2<0,B2/A2,"")
copied down

you need to check for a value in A2 because if A2 is empty then you get a
#DIV/0! error.

HTH
Jean-Guy

"nexxusvp" wrote:

I have a two columns of data in excel (x) and (y). I want to
calculate instantaneous rate of change for values in (y) with respect
(x). How can I do this?

X Y dy/dx
1 10
2 100 ?
3 1000 ?
4 10000 ?
5 100000 ?