I agree with DnvrFox. You don't need an event...just work out a schedule of longer and longer rides and then when the weather is right and you feel right...like the Nike commercial says, "Just do it!"
Events ...be it a bike race or ride or a running race...are nice for the fellowship but you don't need them to accomplish goals. Heck...this spring I did a marathon on a treadmill...just because I could.
Go for it! You can do it!
Jim J