You can control where you edit cell contents in Excel by using the following methods:
Method 1: Use the Data Validation Feature to Restrict Data Entry to a Certain Range of Cells
Step 1: Select the cells that you want to restrict data entry for.
Step 2: On the Data tab, in the Data Tools group, click Data Validation. The Data Validation dialog box appears.
Note: If the Data Validation dialog box is not displayed, make sure that the cells that you selected are not empty, and then click Data Validation again.
(Optional) To give your users a hint about what type of data they should enter in the selected cells, click the [Input Message] tab, and then type a title and message in the corresponding boxes.
(Optional) If you want to prevent users from entering invalid data in the selected cells, click the [Error Alert] [tab], and then select an alert style and type a title and message in the corresponding boxes.