Any formula can use B20. There is no limit. Here are some:
=B20+10
=B20*4
=SUM(B20:B45)
=B20/100
It is the reference to the cell formed where column B meets row 20.
You could use the SUMIF function. The range of cells to add are in the first part of the formula and the condition is enclosed in quotation marks. Say your values are in the all cells in column B from B1 to B20. Then in another cell your formula would be: =SUMIF(B1:B20,">0") This will add all the values from B1 to B20 that are greater than zero.
To make it easier to see what parts of a formula refer to what cells or references on a worksheet, the cell references in the formula are shown in colour and highlights around the cells are in the corresponding colours.
It contains relative cell references.
Relative cell references and some mixed cell references will change when a formula is copied.
It would be a formula that includes absolute references in cells. When such a formula is copied, those cell references will not change. An absolute cell reference includes cell references with two dollar signs in them, like: $A$2.
A formula.
There are several functions of Excel that do not work with 3D formulas. These include cell references and range formula.
Change the formula to use absolute references instead of relative references. Instead of =A2+B3, use =$A$2+$B$3.
Although Excel checks that the formula has the correct structure, it does not check that the formula contains the correct values or cell references.
In Excel it allows you to enter formulas using the mouse, by clicking on cells as you type a formula, instead on typing the cell references.
Use absolute references (e.g. $C$3) instead of relative references (e.g. C3). See related questions for more information about absolute references.