Enforce either upfront payment or Autopay upon sign up

At the start of a season is it possible to have Autopay as an option when they enrol in a class, but require that they either pay upfront or be enrolled in Autopay? (One or the other - we don't want everybody to have to sign up for Autopay as most will pay upfront, but the idea is that those who don't want to pay now have to sign up for Autopay).

In the past we've allowed upfront or they can pay later, but then we have to chase payment later so we're trying to avoid this by making the only other option Autopay... hope that makes sense!