Writing Excel applications in .NET
Same architecture for Excel and WPF / Silverlight applications
Write your underlying business model as .NET code. Make your code readable, testable and evolvable using the MVC pattern.
If you are a fan of building applications using the MVC/MVVM pattern and you love Excel as the user interface for your applications but want to make your applications fully testable, then ExcelMVC is just the component you need.