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Session 12 — Programming with Custom Formulas 157

OR(cond1, cond2). Returns False only if cond1 and cond2 are both False; returns
True otherwise.
Not(cond). Returns True if cond is False; returns False if cond is True.

For more details and examples of using the logical operators, please refer to
Session 5.
Cross-Ref

Avoiding Circular References
A circular reference exists when the formulas in two or more cells are mutually dependent.
Here’s a simple example:
In Cell A2: =B2/2
In cell B2: =A2*10

You can see that the value of cell A2 depends on cell B2, and the value of cell B2
depends on cell A2. Excel cannot calculate when there is a circular reference. If you create a
circular reference manually, Excel displays a warning dialog box. You can then display the
Circular Reference toolbar (View ➪ Toolbars ➪ Circular Reference) which also displays a link
between the cells that are involved. Also, the circular reference dialog box is displayed, let-
ting you examine and resolve the problem. This is shown in Figure 12-2.

Figure 12-2 Excel does not let you enter a circular reference manually.