I followed the instructions on creating an auto-populate field that queries via form load, used this site: http://spvee.wordpress.com/2013/04/10/auto-populate-user-information-in-infopath-with-claims-based-authentication-part-1-of-3/
Works well. However, after form entry, another user must edit (update) the form with status/notes and the user lookup that auto-populates changes to that user's name. How can I lock the auto-populated field after initial entry? InfoPath does not recognize this field as a "field" so no rules can be applied.