Well I'm not in favor of building on the fly. I like to model the data involved and set up proposed tables, then work with test
data and test scenarios to vet the model. You are extremely familiar with your need and data, but the rest of us are not. So we (I) are trying to sort out the essence of your business and decipher your tables and fields. We don't know the details of what is needed in simple English terms. When you have more than 1 field to represent something and under certain conditions, you end up with some convoluted logic to sort out the issue. Often whether or not a representation (proposed structure) meets the requirement can be tested and evaluated with a model and test scenarios.
The best advice I can offer at the moment is to test your theory/intention with some sample data. That way you can confirm whether it works or not. It appears that you may have a design issue based on your concerns with CycleCount. But look at the whole issue, don't add fields or special code to solve 1 issue at a time. Keep the big picture in mind --someone will have to maintain this at some point.
See my stump the model for some ideas.
??Where exactly do you use frmWOSubformLotNumLookUp??