Follow these steps to Enable or disable Edit mode
If you try to use Edit mode and nothing happens, it might be disabled. You can enable or disable Edit mode by changing an Excel option.
Click File Options Advanced.
In Excel 2007 only: Click the Microsoft Office Button Office button image , click Excel Options, and then click the Advanced category.
Under Editing options, do one of the following:
To enable Edit mode, select the Allow editing directly in cells check box.
To disable Edit mode, clear the Allow editing directly in cells check box.
I hope this helps!