I struggled with getting a value list to work using a primary key and showing the second field only of a calculated "full name" field, because the calculation was unstored (to update if the first or last name was changed/corrected). I saw a number of complicated work-arounds, but stumbled upon a seemingly simple solution.
My solution was to create a text field "Full Name" with an auto-enter calculated value of "First Name" & "Last Name" -- and unchecked "Do not replace existing value of field (if any)"
My question is, will this cause problems down the road? It seems to work well in my test file, but I am still learning.