Modules & VBA :: Create Disable Alphabetic Keys Function Based On Case Statement

Details:
I have a Profile form that tracks the expiration date for each client's various certifications. These dates are set up in the Short Date format in the table design of Access.

Problem:
When a user accidentally presses an alphabetic key while updating an expiration date, an Access error message is triggered. This is confusing to my users as these messages are written in Access lingo. I would rather that nothing occurs at all. I wrote a case statement to disable each letter of the alphabet and applied it to the On Key Down Event for each expiration date control on my Profile form to solve this problem, but this must be applied to 28 separate controls. I would rather call a function that disables alphabetic keys for each date control in my form when called.

Questions:
How do I transform my Disable Alphabetic Keys Case Statement into a function that I can call for each expiration date control? I know that when writing a function certain variables have to be declared and/or initialized.

Also, will I need to create a function to re-enable alphabetic keys or is this unnecessary because the disable alpha keys function will only be called for specific controls, not the entire form?

What I Have Tried:
I have tried copying and pasting my Disable Alphabetic Keys Case Statement into a module to attempt to create a function, but it needs work.

Below I have included 2 types of code:
(1) The original On Key Down code applied to each date control on my form
(2) The same code written as an attempt at a function

Original Profile Form Code to Disable Alphabetic Keys in the On Key Down event for each date control

Private Sub txtCert1ExpDate_KeyDown(KeyCode As Integer, Shift As Integer)
Select Case KeyCode
'All message box text is for me to test the code, not for the user to see
Case vbKeyA
MsgBox ("you pressed the A key")

[Code] .....