Split your database (the way a multiuser database should be) and give the
manager a front end with the queries and other users a front end without
those queries.  Make sure that the manager's front end is on his computer,
not a shared one.  Of course, the data is still visible to the users in the
tables but you can hide the tables so they can't see them.

Without user level security you cannot password protect specific queries. You
can't even protect the tables from viewing by others. You can hide the tables
and queries; however, you'll have to assume that all the employees are rather
stupid and can't figure it out.

That leaves three options: (1) don't put the sensitive data in the database
or (2) do full user level security on the database and set appropriate
permissions, or (3) decide that the data isn't no big deal and let everyone
see it.