In the list box at the top of the dialog box, click the option called Use a formula
to determine which cells to format. This selection evaluates values based on a
formula you specify. If a particular value evaluates to true, then the conditional
formatting is applied to that cell.
In the formula input box, enter the formula shown here. In this formula, we’re
evaluating whether today’s date is greater than 90 days past the date in our target
cell (C4). If so, the conditional formatting will be applied.
=TODAY()-C4>90
Click the Format button and choose your desired formatting. This will open the
Format Cells dialog box, where you’ll have a full set of options for formatting the
font, border, and fill for your target cell.
Click the OK button once you’ve completed choosing your formatting options.
Click the OK button twice to confirm your formatting rule back on the
New Formatting Rule dialog box.
