Abstract: Method implemented on a computer of monitoring a supply between at least one supplier and at least one client. A client site has at least one project, each project is associated with dated requirements for products, a state of a stock of the products and purchases of the products being known. The method including creating a list of product types required for each project, and producing at least one table for each product type for a sequence of time slices having a chosen time origin. The at least one table has a first running total for each time slice from the time origin up to a time slice of interest of a first quantity associated with the dated requirements of the client site. The at least one table further has a second running total for each time slice from a time origin up to a time slice of interest. This Abstract is not intended to define the invention disclosed in the specification, nor intended to limit the scope of the invention in any way.