micheleh: is that an option?
It should be. From what I gather you're trying to build a scheduling app where A must be complete and billed before B then C is available. I would look at your scheduling lookup table and add columns to cover complete and billed status. When you poll a customer to figure out the next step, your lookup table can tell you if A was complete and billed. Ideally you have one table with minimal columns you can use to poll a customer quickly - use this table to get critical details like status, billing and their record_id.
Hope this helps,
~C