Web Identifying events with ticket availability

We're looking for a way to identify performances with ticket availability, in order to display dates as links (or not if a performance has sold out). This needs to be dynamic, and not rely on a manually set flag (eg, On sale indicator). We've looked at:


"gross_availbility" and "availbility_by_customer"

But they both return zero when there are tickets available. Anyone know how these work, or if there's a better call to make?

Thanks, Christopher