Insert upsell page after CoursePress Pro sign up

Hey guys,

Discovered your services through AppSumo and I love it. I've used a lot of your plugins in just a month and really like features you offer and how you offer them.

I have a bit of an advanced question, I'm planning on selling a course online (so I'm using CoursePress Pro and MarketPress).

I want to generate leads with a free course that give value and create a bit of familiarity with the learning process and medium.

Now, I'd like to insert an upsell page right after the signup (for the free course) is confirmed.

Ok, it's not really an upsell as I won't have sold anything before but I want to use the momentum of the user registration to put a one-time offer at this very moment.

If you have a suggestion, even a programmatical one (on what kind of hook should I look into, ...) I'd love to hear about it.