How to associate a webform submission to quiz results?

In my use case, anonymous users fill out a webform before they can access a Multi-choice quiz. I need a way to link the webform submission that contains the quiz taker's data (first name, last name, etc.) to the Quiz results. In other words I would like to add to the results a reference to the form submission.

I had a look at he API but cannot tell if there's a hook that would fit my use case.
Any suggestions as to the best way to accomplish this?