cck compute user reference

I'm struggling to come up with tidy little snippet for a computed field to interact with the user reference module.

The big picture:

• I use profiles for Department Faculty so that they can log in and manage their own info.
• In order to link content types I want to associate with a particular faculty person (say, a book section), I add the user reference field.
• I find it handy to sort by the faculty member's last name, so I want the computed field module to pull the value from the user-reference field and trim it.

I've been searching for an example of getting the UID out of the CCK user reference module and used in the CCK compute module with no luck. Either I'm searching for the wrong stuff, in the wrong places, or an example of this is not out there. Can anyone help me out?

A generic example is fine, but my specific need is to take the 2 users selected from the cck user reference module and on the same node compute a field that takes the first and last names from a custom profile and concatenates them.