In this chapter we look at integration with Microsoft Excel using COM. This is interesting for technical and business reasons. Technically, it will give us a chance to look at both server- and client-side COM. On the business side, we’ve built a financial application, and a vast amount of financial data comes from and ends up going back into spreadsheets. We’ll develop some simple examples that allow you to import and export data from spreadsheets, and see how to build an alternative frontend for pulling out data in Excel.