>>If you can guarantee that no bit is set more than once, you can simply sum these fields.
>
>I thought of that, but, unfortunately, can't make that guarantee--pretty much the opposite, in fact.

Then you are having multiple assignments for the same time slots - which doesn't necessarily mean your data are bad, it's just that your rules have a definition of assignment which doesn't help here :).

It's either scan/endscan with a BitOr() then, or having an actual child table with taken slots per record and SQLing from it. Which I assume you may actually have somewhere, because you surely don't just mark the assigned/unassigned status for the slot, you probably have some other data, like assigned for what, where, what resources are needed (in the PPT - places, people, things category) or reserved. And you don't need to have records for any of the free slots, only for the occupied. You can always right outer join whatever cursor you need with a blank template cursor with free slots.