I have a request for some contract work from an organization that uses Excel as a database and wants to do some work on the Excel data via a real database. (Yeah, I know, ne
Excel is a 'COM Capable Application' and as such you can use COM to access and manipulate the data in an Excel document. You don't say what platform you are using - but if it's .NET then it's really very easy. See http://support.microsoft.com/kb/302084 for how to get started with C#.
If you're not using .net then any language that can interact with a COM component will work.