You want EPDM to read a table in a drawing and override the calculated quantities automatically? You aren't actually modeling assemblies A and B with the correct quantities of X?
It is going to take some API programming to read the tables and update quantities.
Sorry I should have noted this...
The assemblies can have tens of part X to tens of thousands of part X, so for the assemblies become unmanageable at higher quantities of X. So no, I am not modeling the correct quantites in the assemblies
I could live with an API script to update the QTY in the BOM table but wasn't able to figure out how to do that without creating a custom column in the BOM table, which then required me to update the BOM QTYs for all parts in the assemblies.