A software tool enables sales organizations and sales representatives to graphically track past purchases from customers, as well as the customer's current holdings and install base of products and services, irrespective of whether the current holdings originated from the sales organization, from a competitor or from some non-competing supplier of goods or services. By tracking not only past purchases, but the totality of the customer's holdings, the sales representative may draw inferences from the customer's current installed base of products, identify new opportunities and potentially sell additional or complementary products to the customer. The tracked information is stored in a central repository such as a database, enabling the employer to maintain control over the information, thereby enabling the information to persist even after the sales representative has left the employ of his or her current employer. The central repository is preferably selectively available over a computer network, via a Web browser, for example.