This paper describes the application of online analytical processing (OLAP) in the field of data mining. We discuss knowledge discovery in enterprise databases as well as data warehouses. We then present an enterprise decision modelling application. This internet application stores requests, mistakes and defects that are notified by customers for software modules. Data are retrieved from Oracle database by using Microsoft Excel. Excel's interactive visual interface helps to build data cube and get graphics for executive managers. This OLAP application is applicable to any ecommerce or supply-chain applications which accumulate huge data sets in order to have the potential to yield more valuable information. KEYWORDS OLAP, data-mining, data warehouse, decision modelling.