Standards or guides for documenting EXCEL calculation templates?
 

I use EXCEL for numerous calculations; most include a lot of data and contain
a number of calculations (mostly with formulae in cells) and data operations.
The files are saved and used repeatedly, with both new data and with
modifications to the calculations. Is there a guide, standard or recommended
approach for documenting the calculation using EXCEL features such that an
independent user could easliy understand the template design and function and
use it for the purpose intended?