Luca Bolognese has released a .NET library that provides the full set of financial functions from Excel. The main goal for the library is compatibility with Excel, by providing the same functions, with the same behavior. Note though that this is not a wrapper over the Excel library; the functions have been re-implemented in managed code so that you do not need to have Excel installed to use this library.
More here including the download links: http://blogs.msdn.com/lucabol/archive/2008/12/04/financial-functions-for-net-released.aspx

Denis has been working with SQL Server since version 6.5. Although he worked as an ASP/JSP/ColdFusion developer before the dot com bust, he has been working exclusively as a database developer/architect since 2002. In addition to English, Denis is also fluent in Croatian and Dutch, but he can curse in many other languages and dialects (just ask the SQL optimizer) He lives in Princeton, NJ with his wife and three kids.