You can add custom functions to Excel (e.g., the ribbon) and other Office apps using Visual Studio Tools for Office (VSTO). There’s almost nothing you can’t do

You can add custom functions to Excel (e.g., the ribbon) and other Office apps using Visual Studio Tools for Office (VSTO). There’s almost nothing you can’t do once you have C# or other .NET languages in the mix (I like to use F#). One of my collaborators (Ben Zorn) is one of the people featured in the linked article. We’ve been working on visual debuggers (and other things) for non programmers in Excel for a few years now.