Self paced course with dynamic end date - help pls

[michaela honer]

hi everybody. i've finally managed to install an server and the hawthorn.2. now i do have a question. i would need to define a SELF PACED course, which HAS to be completed in 90 days, else it fails. so no dates, people can enroll every day, but they only have 90 days to complete the course. Is there ANY solution to this problem? Thanks much for your time. Best Michaela