Simple thing is to create a page alias and have the repeater use that alias as a query string. For instance /Events/{EventType} as the alias on the Events page.
Then in each button you'd create a link that was simply <a href"/Events/Current">Current</a>
and <a href="/Events/Upcoming">Upcoming</a>
. This would be assuming the categories you stored were "Current" and "Upcoming". Then in your repeater where clause, enter something like EventsCategory = '{%EventType%}'
Each time you click the button, it will simply send you to that link and the repeater will get the values based on the query string.