If you are a fan of building applications using the MVC/MVVM pattern and you love Excel as the user interface for your applications, then ExcelMvc is the just component you need.
ExcelMvc lets you write Excel applications like writing WPF or WinForm ones using the MVC/MVVM pattern. You define your application's views in Excel and implement their business models and view models (controllers) in C# or any other .NET languages.
ExcelMvc also lets you write your own high performance user defined functions (UDF), including RTD functions and asynchronous functions.
Simply add ExcelMvc.Net NuGet to your solution to get your ExcelMvc development started.
https://github.com/triaxia/ExcelMVC/tree/master/Docs/Getting%20Started%20with%20ExcelMVC.docx
More documentation can be found within the sample solutions.
UDF samples:
MVC samples: