Unfortunately, this is not available in JOIN just yet. We are working on a possibility for this and hopefully, it will be available real soon.
What you can do is, set your first goal in JOIN and train towards it and after your race, you start your next goal, and JOIN will ensure you are in your best shape for both.
If you are racing every weekend, I would suggest you enter your main goal as a target or follow one of our training programs. Weekly you can then add a 'quick ride' on the day you are racing and JOIN will take this into consideration, you can also set your availability to '0' the day before your race to ensure you can do an easy ride and be ready for your race.
For more information on how to add a planned ride/race in JOIN, see this link - https://help.join.cc/hc/en-150/articles/5882815770257-How-to-add-planned-Quick-ride-in-JOIN