As we need the help of others to enter a datasheet together, how can we make the collected data formatstandardized and accurate?In this lesson, we've learned how to restrict the cells' contents through Data Validation.

1. What is Data Validation?

- Select the cell area and click the Data tab> Validation,  there you can select different conditions in the dialog such as Date, Text length, Whole number, or limit the duplicate values. Through different conditions, you can limit the formats and contents of cells.

2. How to turn on the Error Alert of Data Validation?

- If the cell entry rules are limited in advance, it is best to set the corresponding error alert, which can remind you to enter the correct format according to the alert. In the dialog box of Validation, click the Input Message and Error Alert to set the corresponding reminders.

- Also, we can circle incorrect data against rules in the table. Select the table area, click the Data tab> Validation> Circle Invalid Data, then you get it.

PS: At the end of this case, we also learned how to create an associated multi-level drop-down menu through the INDIRECT function.