isaacson,
As Julie notes, Project has no functionality to do what you want, at least not in the way you're asking. I see a couple of possibilities. First, this could be done with some VBA but it wouldn't necessarily be trivial. Another thought was to create resource
groups for those resources you want to pair, so instead of saying Joe and Bill are assigned to move the piano, set up a Team1 resource that consists of two people, in this case Joe and Bill. Then you assign Team1 to the piano task.
Granted, the latter approach gets a bit messy if Joe and Bill also have other individual tasks. It depends on your overall plan structure as to how "challenging" that will be. You might be able to accommodate this by assigning the Team1 resource at 100%
(i.e. one half the team) to those individual tasks and then using leveling to avoid overallocation, or manually edit the overallocation conflicts. Of course, you wouldn't be able to identify which half of the team resource was assigned to an individual task.
One other fringe idea pops into my head (that's the problem with asking a question on the weekend, you get the really off-the-wall ideas). It might be possible to set up a custom work calendar for the paired resources. It would take some effort because
you would have to edit each resource's calendar anytime a change was needed.
Just some wild thoughts.
John