Excel’s preset conditional formatting is great for most conditions, but if you want to set your own parameters and formatting, you can do so by creating a new rule.
Select the cells to which you want to apply your conditional formatting.
On the Home tab, click the Conditional Formatting button, and choose New Rule from the gallery to display the New Formatting Rule dialog box.
Enter the information required for that rule, using the values and formatting you want. Each rule requires different types of information.
Select the formatting you want to apply to the cells that meet the conditions you’ve set. If the dialog box contains a Format button, click it, and, in the Format Cells dialog box that appears, specify the formatting you want. Click OK.