Problem updating from a different repository

Hello,

I'm a CVS newbie and having problems working with two different 
repositories on the same working copy.

1. I have a working copy checked out from a local repository (REP2 under 
/cvsroot).
2. Now I would like to update this copy of the module from a remote 
repository (REP1 remote server under /home/cvsroot). It is a repository 
where I don't have a write privilege, but where the actual HEAD version 
is contained. My local repository is just for keeping track of minor 
changes I apply to the source.

After having read the docs and the archives to this list, I still don't 
understand how I could update my working copy from the main repository 
(REP1). Whenever I try this, I get a "cannot open directory" error.

Is it because of the different relative locations (/cvsroot <> 
/home/cvsroot) of the repositories.

Thanks in advance for any hints!

Michael