Guide

1. Inside your Microsoft Excel worksheet, find and select the cell containing the drop-down list you wish to edit.

2. After that, navigate to the top menu bar and then click 'Data'.

3. Select 'Data Validation' from the available options.

4. Next, click the "Source' input field and make your desired changes. You can reselect the cell range you wish to use or type the cell reference manually.

5. Once done, click 'Apply' to proceed.

6. After completing these steps, the source of the selected drop-down list will be updated based on your input.