create a field that display value from an other one?
I'm not sure this is suited to your needs but maybe the entity reference module might be able to help you :


  Provides a field type that can reference arbitrary entities:
  
  A generic entity reference field Four widgets:
  Two implemented on top of the Options module (Select and Radios/Checkboxes),
  Two autocomplete
  widgets (one with one text field per entry, one tag-style with
  comma-separated entries in the same text field)
  Two formatters:
  A
  "Label" formatter, with optional link that displays the label of the
  referenced entity (the node title, the user name, etc.)
  A "Rendered
  entity" formatter, that renders the references entity using a
  configurable view mode Integration with Views (for both forward and
  backward references)
           Integration with Entity Metadata (and as a
  consequence with Search API and the like) Integration with Devel
  generate Integration with Feeds and Migrate (>= 2.3) for painless data
  import This modules depends on Entity API and CTools.