I found this trick during the development of Acton Institute's new Drupal-ized website.  I wanted to be able to list out other articles by the same author and show it on a sidebar.  Here's the setup:

• Article authors are CCK nodereference fields to a separate author content type

How does one then construct a view that thinks the author is a CCK field and not the actual node's author?  It's a lot easier than I thought.  The only thing you need to have in your view is an argument with a little PHP magic.

• Create an argument and locate your author field attached to the article type you'll be showing this view on (I do it with block visibility)
• Select "Provide default argument"
• Under "Default argument type" select "PHP Code"
• Paste this in the box, replacing field_author with the machine-code name of your field:

$node=node_load(arg(1)); 
if($node) { 
     return $node->field_author[0]['nid']; 
} else { 
     return FALSE; 
}

• I have Action to take if argument does not validate set to "Basic validation" and "Action to take if argument does not validate" set to "Hide View / Page not found (404)"
• "Allow multiple terms per argument" is checked.
• "Exclude the argument" is unchecked.

I then added a block and set it to only show on certain articles.  When visitors go to an article they can see the latest articles by the author of the article they're viewing.