ATP with Allocation Rules - Inventory Update more frequently

If we run a targeted update on Inventory tables will the existing ATP plan (with Allocation Rules) use that information or does it have to wait for a new ATP plan to run. We have the issue that someone tries to book an order and there is no inventory present, then they process a return so have inventory but can't allocate it to a customer until the next day. Any other solution to this?

Thanks,

Jeri