1. select whole worksheet
2. right-click mouse and select the "format cells" option
3. click the "Protection" tab
4. untick the "locked" and press OK
5. highlight the cell the want to protect
6. right-click mouse and select the "format cells" option again
7. click the "Protection" tab
8. tick the "locked" and press OK
9. go to tools -> protection - > protect sheet
10. assign password
11. OK
