Prevent Typing in Drop Down List Cells

I'm trying to prevent users from typing in a cell which has a drop down list through data validation. Can anyone suggest some code to accomplish this?

The issue is that if you type something not contained in the list Excel 2010 gives an error message and then the user can click "Retry". However Excel doesn't clear the cell and the user is unable to access the drop down list unless the cell is clear.

My other thought is possibly some code that reacts to the data validation message and clears the cell when they select "Retry", but I couldn't find anything regarding that type of event.

Many thanks!

Thanks for the suggestion but I'm trying to avoid additional instructions for the user as much as possible

Just turn off the error messages. No message means no retry to click. it's the error alert tab when you create/edit the data validation.

I don't think that will fly either, I'm really looking for a more elegant solution involving VBA rather than a workaround

Turn off the error messages, script in on the worksheet_change to detect if the value is in the list or not, then use script to clear the box and/or give them a message box telling to pick from the list. See the attached.
list message.xlsm