Does anyone know if it is possible to "Fill Down" or "Fill Right" with a cell
formula without changing *all* of the cell references in the formula?

For example, I want to compute a set of averages by dividing the sum of an
array by a the contents of a cell containing the total number of values. My
original cell formula reads "=sum ((A1:A10)/A11))". Is there some way to
allow the "A1:A11" reference to change to "B1:B10" with a Fill Right command,
but keep the "A11" reference constant (i.e., not changing to "B11"). I often
run into wanting to compute values that include "constants" obtained from
other calculations.

Is there any easy fix to this, short of a cumbersome search-replace routine?