Group of CCK fields assigned to the same NID without an additional Node type and Node referrence
It appears to me you are needing a compound CCK field type.

If so, take a look at http://poplarware.com/articles/cck_field_module for a rather in depth discussion of how to write your own. 

If you don't want to do that, the 3.0 branch of CCK for Drupal 6 apparently has a Multigroup Module.  Check out How to add cck custom date field? for discussions about that option.