I made my own by;

1. Make a new table and create a field called whatever.
   If your app will be shared over a network, include the
   table in your app, not on the server.

2. Make a neat little popup form with the recordsource
   set to the table you made. Include a textbox(linked to
   the field) for the user to put the code in and a
   command button to close the form. Set the border style
   to "none"(this gets rid of the min/max/close buttons
   completely, there is a know issue with the close button)
   Use the before update event of the textbox and put
   some code in to validate what the user has entered. I
   gave them 3 chances to it right and if they failed, I
   terminated the app and deleted what they had entered,
   if they got it right, I saved the record and closed the
   popup form.

3. In  the mainforms on open event, open the popup as
   hidden and check to see if the textbox is null or not.
   If it is null, then show the popup, if it isnt, close the
   popup.

This worked fine with my app and I havent had any issues.

If you want to keep your code string a little private, you
can set the property for the field as a password, even though
people can download software to view passwords, the average
jane doe wont think of it.

Need help post back.

David W