Invite Code Needed For All Sites?

I am using the WPMU Dev Membership Plugin, and I need to make it so an invitation code is required regardless of whether the user is already a member or not. This is to protect content from being viewed. The subscription itself is free, however I need for them to have to enter an invite code each time, rather than be able to skip past it due to membership existence. How can this be done? This is a necessity.

And then I discovered the edit button :

Okay, so, my reply below explains it further in depth.

Summary of the below post:

So basically what I need is:

– Invite code needed every time

– Invite code attached to subscription type(s) (multiple codes for different subscriptions/memberships)

– Invite code generator with flexible variables

– Information on how to change the invite code text to something other than invite code without breaking the plugin