Import question

[Lemke, Michael IZ/HZA-IOP]

When I do a cvs import of a new vendor version the new files become the
head revision.  I'd like to do the import such that it doesn't affect HEAD.
Only after I've tested the new stuff I want it to become HEAD.  Of course,
it should work with local changes merged in just like the standard way of
doing it on the trunk.  How can I do this?  

Thanks,
Michael