How to add "Date Closed" to module

Hi all,

Was wondering how complicated it would be to add a “Date Closed” parameter to one of our modules?

I’ve tried to add it as a label and a field but I think I’m looking in the wrong area. “Closed” is a variable that is within a drop down when we close select the status of a particular case with a client.

I’ve the sort of thing I need in green below:

Thanks in advance!

@Troika

You can use custom JavaScript code for frontend and workflow or logichook for backend.