Why do I get an "Unprotected Formula" message?
There are two possible situations in which you might see this message:
You see a green triangle in the upper-left corner of a cell that contains a formula.
You are evaluating errors in the Error Checking dialog box.
By default, all cells are locked to protect them from accidental or unauthorized changes. In this case, the cell containing the formula is not locked for protection.
Lock the cell by doing one of the following:
Click the Error Checking button next to the cell, and then click Lock Cell.
In the Error Checking dialog box, click Lock Cell.
Protecting cells that contain formulas prevents them from being changed, and can help avoid future errors. However, locking the cell is a first step, and you must perform additional operations to protect the workbook, such as setting a password.
For more information about how to protect a workbook, see Protect worksheet or workbook elements.
For more information about how to control error checking, see Use error checking to correct common errors in formulas.