How track employee referrals on candidate profile, not each job application

My company keeps employee referrals on file for 6 months. How are others tracking these referrals to ensure that the referral follows the candidate across multiple job applications? I'm looking for ideas on how to ensure that both manually updated source information (for times when the recruiters must manually add the referral) and referrals generated through the internal opportunities marketplace stay on the candidate's profile and therefore show up on each job application thereafter.

For example, Employee 1 refers Candidate 1 to Job Requisition 1. The candidate is not selected for that position, but applies for and successfully is hired for Requisition 2 (or the recruiter submits the candidate to Requisition 2). How can we ensure that Employee 1 remains the source for this candidate?