cvs diff without local copy

[kaosmaki]

Hi,

I'd like to run a cvs diff w/o having a local checkout. I read I can
use two -r options as follows:

cvs diff -R -r $TAG1 -r $TAG2

But how does cvs know, which module to take? For now, I have to cd into
the correspondig directory of a local copy, even it is not used during
the diff at all.

Is there a way to avoid using a local copy and to tell cvs otherwise
which module to take?

Sincerely
Matthias Baerens