Just looking at how we might make a product visible only when an existing product is due to expire. For example, a user purchases a product which is a three month training course. At some point just before the expiry of that, we want to make a product available that they can then purchase - an extension course for another three months, for example. Each person might purchase the original product on different dates, so I want to be able to reveal a product at a specific time relevant to each user... i.e two weeks before expiry, or whatever. Is this possible?