PeopleSoft Recruiting - Add a tag/code to a Job Opening URL

We are working with an external vendor to attract applicants by posting our jobs to other job sites, they normally get the applicants and redirect them to our career site to complete their application.

This works well but a new vendor is requesting us to add a custom tag or string of text appended to the job URL to track the referral source.

Has anyone done anything similar that can provide us some guidance?