Editing Formulas
After you’ve entered a formula, you can (of course) edit that formula. You may need to edit a formula if you make some changes to your worksheet and then have to adjust the formula to accommodate the changes. Or the formula may return an error value, in which case you edit the formula to correct the error.
The following are some of the ways to get into cell edit mode:
- Double-click the cell, which enables you to edit the cell contents directly in the cell.
- Press F2, which enables you to edit the cell contents directly in the cell.
- Select the cell that you want to edit, and then click in the Formula bar. This enables you to edit the cell contents in the Formula bar.
- If the cell contains a formula that returns an error, Excel will display a small triangle in the upper-left corner of the cell. Activate the cell, and you’ll see an Error Checking button. Click the Error Checking button, and you can choose one of the options for correcting the error. (The options will vary according to the type of error in the cell.)
Tip
You can control whether Excel displays error indicators in the Formulas section of the Excel Options dialog box. To display this dialog box, select Office Button 
Excel Options. Click Formulas. If you remove the check mark from Enable Background Error Checking, Excel no longer displays the error indicators or the Error Checking button.
While you’re editing a formula, you can select multiple characters either by dragging the mouse cursor over them or by pressing Shift while you use the direction keys.
Tip
If you have a formula that you can’t seem to edit correctly, you can convert the formula to text and tackle it again later. To convert a formula to text, just remove the initial equal sign (=). When you’re ready to try again, type the initial equal sign to convert the cell contents back into a formula.