Hi Maria
I sympathize. This is exactly the reason to incorporate security asap. How do you know that people are not chopping and changing data, tables and relationships?
Why not set up security and remove the "admin" user (this is the default user). This will prevent anyone unauthorised from connecting to your database.
Another one (which is well worth doing) is slapping a database password onto the database as well (this will slow down anyone thinking about taking advantage of you and your hard-earned work.
Firstly, though, try and do this when noone is around, and make a copy of the database (maybe to CD?). This will ensure that if anything goes wrong, you can always restore the old version. I would suggest doing so after work or during lunchtime when noone is around.
In order to see who is using your database, that depends on the network setup you have. The old Novell Client32 had a "whohas" command which would tell you who has a connection to that database. You can always back the database up to CD, then delete the backend and wait for people to come crying to you! This is cruel, but its no different from the way that they treat you.
Mr Big.