can particular cvs project files be locked/ignored

[Mark]

There are a few files in our project under cvs control
that are going to be in a frozen state from now on and
that we don't want to cvs remove and then attic (at least
not right now)
By frozen, I mean that if external files of the
same names are copied on top of them in someone's sandbox,
I don't want cvs update to try to merge them but rather
I'd want a cvs update in the directory to either ignore
the files or just say "file X is locked" or something
similar.  I looked in the cvs pdf manual I have but
didn't see a obvious way to do that. I can't 
use .cvsignore files because that's for making
cvs ignore files that are not in the repository but
which need to be in the local work directory.

Mark