You want to create a validation rule to prevent the user from accidentally entering a negative value. For now, you will create a validation in the Friday worksheet.

Select the range E$5$:E$24$ in the Friday worksheet, create a validation rule to allow a decimal value greater than or equal to zero. Enter the input message title Tip and the input message Enter the amount of tip. $($including the period$).$ Use the Stop alert with the error alert title Invalid Number and the error alert message The tip must be zero or more. $($including the period$).$ Test the data validation by attempting to enter $-20$ in cell E$5$ and then cancel the change.