Put the value in a cell then all you need to do is change that cell and not
the formula.

A1 = 3

=SUM(M13:M16)/A1

Biff

"Donnas" wrote in message
...
This may be really stupid questions but here it goes...
Below is my formula, I am adding some columns then dividing by 3. Next
week I will need the same columns added but will need to divide by 4, the
follwing week by 5. Is there any way Excel will do this without me
manually
changing the number each week?

=SUM(M13:M16)/3