This is absolutely possible and very easy to do.
The way the question is worded however,  I don't know that I would advise that you do it.

It sounds like:  1. This isn't your database - you didn't develop it.  2. You haven't worked in developing a database let alone this one in Access before.

Not knowing a lot of things about your database, how it is designed, and how it is setup it is very difficult to advise you on how to accomplish what you need to do.  I wouldn't want to have you break an otherwise functional and working db by getting in and poking around (if you even can - it might be locked down for editing.)

The first thing I would have you do is contact the original developer first.
If that is not possible we'll need to have a lot more information on your set up.

Unfortunately the creator of the databases recently passed away. If you can email me I could give as much details that I can. [email protected]. This database has macros its for a membership database.

Sounds like you just need to set a default value of no that they don't have a key and then if they do have a key the user can manually click on the yes box.