NorwichH8R,

The way I handle licensing, renewal notifications, expirations, and
re-licensing,
is by using Windows Explorer, click on your workbook, and select properties.
You'll see three tabs marked General, Custom, and Summary. Select Custom and
define a couple of attributes like License, Expiration, and whatever else, and
give them some initial settings. Then in the bowels of your program code
reference them through instructions like

With ActiveWorkbook.CustomDocumentProperties
ExpirationDate = .Item("Expiration").Value
'code here to compare the expiration date against today's date and issue a
notification message, or deny
access if the expiration date has passed
LicenseNumber = .Item("License").Value
'code here to test validity of license number and compatibility with expiration
date

When users renew their license, send them the new expiration date and revised
license number that they use to update the previous ones. You can have them do
this manually, because even if they see where
the new extended expiration date goes, the new license number must be in
agreement with it. Naturally, your program code must be locked, and even though
it's possible to break, 99% of your users will not want to attempt doing so.

-- Dennis Eisen