Hi there, @jeronimo… if I was doing what you described, I would probably simplify things by having a percent sold field on the Event data type, and I would update that field (likely using a backend workflow) every time a ticket is sold for an event. The way you have it now, I believe you would have to use an advanced filter, and that would probably be pretty inefficient because the search would return all of the events to the client (browser), and then the calculation in the filter would be applied to get the right events.
Anyway, just food for thought there, and I hope it helps.
Best…
Mike