how to add password to MS access database

A problem in my work:

We have a MS Access database to manage our machine system. A problem is that anybody in my work can look through the codes and change them by accident or on purpose. This is not good. Changing code may cause loosing data permanantly. I plan to add a password to the database, so that nobody can change codes withoud password (but they can still read/write data in the database). Can anybody tell me what I should do to add password to the database to protect codes from changing accidently.

I appreciate your help.