You can create a small Text File that the program must "read" prior to opening for use. Place the text file in an obscure location in the computer system.

When the deadline date arrives, have your program delete that small text file. If the text file is not present when the program is run the next time - it fails to fully open for the user - just closes itself.

You can do the same thing with a REGISTRY entry.

You could also perhaps have the workbook delete itself upon expiration date.

Bottom line though, if someone wants to bypass your workbook security settings, they will manage to do so. Excel is not very secure.