Mark, I can probably help here but I do not fully understand what you are trying to accomplish. As a general rule, independent pharmacies do not purchase inventory direct from pharmaceutical manufacturers. Instead they purchase from wholesalers such as Cardinal or McKesson. Large chains also purchase from wholesalers, but may purchase certain drugs direct from the manufacturers.
Prices for drugs, particularly generics, fluctuate, which is why non cash (meaning not funded insurance patients) transactions adjudicate using a price schedule which price using a semi-complex pricing algorithm with a pharmacy benefit manager.
I'm happy to share a conversation to try to help answer your questions.