As well as protect a workbook, or a worksheet, (as I have written about that here) you can also create layers of protection by using the Allow Users to Edit Ranges feature in Excel.
This allows you to protect a range with a password.
On the Review menu, next to the Protect Workbook button, is Allow Edit Ranges. (Shortcut keys Alt, R, U1)
When you click this, you get a dialogue box which allows you to set ranges of the spreadsheet and apply a different password to each range.
In this dialogue box you can create the ranges that you want to specify and set the passwords for each one. You can also set the permissions, so that some people, or groups can edit the cells without a password. This works in an organisation. The cells need to be locked and you need to allow the user to select locked cells when you do the worksheet protection.
You can also tick the “paste permissions information into a new workbook”. This will create a workbook with a list of the ranges and the permissions so you can keep it for your records. It doesn’t list the password, so make sure you keep that in a safe place or remember it!
You can modify or delete the ranges you have set up with the appropriate button.
As usual, none of this makes any difference until you Protect the sheet, which you can do with the button on the dialogue box, or on the Review menu.
So, now you can create layers of protection that allows different user to edit different cells as their permissions allow.