How to identify form data that is submitted on a particular dynamic page?

We sell a single product. Suppose we have two sales reps – let’s call them Leja and Peter. I’d like Leja to have her own landing page and Peter to have his.

Leja and Peter carry business cards which they give to the sales prospects they meet. Their cards have sale rep-specific QR codes which, when scanned, take the prospective buyer either to Leja’s or to Peter’s unique landing page.

When one of Leja’s prospects visits her page and fills out a simple contact form, the form fields are submitted with a hidden (extra) field containing a value that is unique to Leja – this is her prospect, not Peter’s. (Or, Leja has her own collection that is completely separate from Peter’s.)

In this way, we can associate prospects with sales reps.

I’m sure that the sales rep’s landing pages are dynamic, but how do I make a form that either submits extra identifying data per URL or submits to a sales rep’s own collection? Do I use a hook in page-specific (unique URL) code to populate a “salesRepName” field, or can I associate separate collections with a unique sales rep?

Thanks for your help and hints.