In one embodiment there is provided a system for recalculating a formula previously used in preparing a mixture made from adding at least two components. The architecture includes an inter-architecture network utilizing a single protocol, a plurality of border elements in communication with the inter-architecture network and with an external network, and one or more call control elements in communication with said inter-architecture network. When filling the therapy bag, the pharmacist, using his computer to comply with standards, simultaneously programs an EPROM with data specifying the Rx as well as instructions for dispensing the Rx. An estimator is then used to estimate an apply boundary deviation or a release boundary deviation of the spool valve, as appropriate.