Abstract: Add-in program instructs operable through a general purpose spreadsheet program in a personal computer to move real-time status and control messages directly between cells in the displayed spreadsheet and addressed registers of programmable logic controllers (PLCs) is disclosed. The PLCs operate such as machine tools for processing stations and connect together and to an interface card in the personal computer over a network. The invention facilities a user's real-time monitoring and control of the manufacturing performed at the machine tools or processing stations through mathematical and logical features of the spreadsheet, which are well known and easy for a user to implement.