To prevent changes to your drop-down list data, you can hide the columns, rows, or the entire worksheet that contains the data. And unhide them if you need to make changes. You can also lock and password protect the cells on the worksheet or even the entire worksheet.
Lock cells to protect them
Your boss wanted you to protect a workbook, but she also wanted to be able to change a few cells after you were done. So, you unlocked some cells. Now your boss is done, so you can lock the cells. Here's how.
Select the cells you want to lock.
Click HOME, then click the Format Cell dialog box launcher (the arrow to the right of Alignment in the ribbon).
Click the Protection tab, check the Locked box, and click OK.
Click REVIEW > Protect Sheet or Protect Workbook, and reapply protection.