Thank you for your help, first of all. I'm setting up an Incremental Content Delivery to sell a three-day course (one lesson per day: it is just a test for major courses). I protected one folder where I put three pages. Each page contains a lesson: 1, 2, and 3. Each lesson is a product. Customers subscribe to Lesson 1 which lasts 5 days: on Day 1 customers access Lesson 1 until Day 5; on Day 2 they also see Lesson 2 until Day 5; and on Day 3 they also see Lesson 3 until Day 5. Fine, that works. The problem is that if a customer knows the links of following modules, they can use them: on Day 1 in the Member's Area only Lesson 1 is displayed, but if I enter the URLs of Lessons 2 and 3 I can get them on Day 1! Therefore customers who get links from friends can subscribe for Day 1, download the entire course, and unsubscribe, paying only Lesson 1 (or nothing, if there is a free trial period). Any idea to fix this problem? Thank you very much.