Here is an alternative that you can use to display a message when a cell is selected with either the mouse or the keyboard.

Select the cell where you want to see the message.
Click on the Data menu and select Validation.
Select the Input Message tab.
Put a check mark in the 'Show input message when cell is selected' field.
Type a heading for your message in the Title field. This text will appear in bold at the top of your message.
Enter your message in the 'Input message' field.
Click OK
Now, anytime you move to that cell, the message will pop up. If you develop workbooks for other users this is great tool to use to help them know what to do.