We use this for our customers all the time. We create a file in the
lists directory called "listname.mod" (with "listname" being the name
of the list), then we put listname.mod on the restrict_post line of
the list's config file. Then the addresses in the mod file can post
without approval while all others are bounced.
However, this can only be set up by someone who has majordomo admin
privs and can create and edit files in the lists directory. If you
don't have those privs, you'll have to ask those who do to set up the
mod file for you.
And the actual file name is up to you. We chose listname.mod to
signify it was sort of a list of 'moderator' addresses.