The formula likely to exist in D18 is C , that is B18*$B$13. This is
called mixed cell referencing, whereby absolute and relative cell referencing
have to get combined. For example, the values in the first part of the formula
keep changing, that is called relative referencing. But, when dollar signs
surround a cell in a formula it becomes absolute referencing, its value remains
constant matter where it gets placed on the sheet.
