all, I'm planning on using Membership for my website, but

Hi all,
I'm planning on using Membership for my website, but I'm just not sure if it's going to work for me. Here’s exactly what I’m trying to do. This website is for teachers who teach a specific method of music instruction. Once they become a licensed teacher, they need to continue to purchase training materials, in a specific order, as they progress as a teacher. There are about 40 or so levels of materials that they will purchase throughout their career.

I’m also using marketpress on my site, which is how the teachers will actually purchase the license to new materials. I’m not using marketpress and membership together, since each teacher will have to be approved for each level, based on their pre-requisites.

What I need to happen is this. A teacher orders the license for level 4, I then go in and manually add them to that specific level that they will be a part of so long as they are a teacher. As a teacher is subscribed to each level, they also retain access to all the previous levels they have already purchased.

What I want to do is build all of the access levels that I need and manually add or remove teachers from those levels, based on what they are able to purchase. I don’t want teachers to have to subscribe to levels because they may not have met the pre-requisites for that level.

Since I’m not going to be using subscriptions for this site because uers won’t be getting several levels at once, is it possible to do this without having subscriptions and without users having to register for each different level?

Thanks in advance.