Hi Jean-Philippe,
This use can be modified to work in many different ways. You can create different If>then>else columns with different settings that give the specific roll up you are looking for. In my example above it SUM would give the total number of paid orders while COUNT would give the total number of orders. I didn’t fully understand what you are looking to achieve and don’t know how you have your columns structured so I couldn’t provide an exact solution.
I was hoping my example would spark some thoughts for ways you could use that work around for your specific app use case. I hope this helps to clear up my intentions. 