Howdy barn2media,
I would love to help you with that. I actually have a great starting point of code for you. It is a simple modification of existing snippet. It will no doubt require further testing and modification on your part, but the principle behind it is that it hooks into our tribe queries, if this is not the admin area then it adds an extra WP Query param that hides events whose end dates are before the current server time. Simple enough aye? Hopefully that will work for you. You might have to add some extra logic for edge cases and stuff though, so test the code thoroughly.
Does that all make sense? Did that work for you?
– Brook