Thank you very much Jo-Anne for your answer,
i tried it on a simple substract between two dates and it's working perfectly, but now i have one more complicated one to realize, i tried to do
the same method but it didn't worked, it will be awsome if you can help me with this one
i'm try'in to do this in my field : (Today() - PlannedStart) * Amount / ((PlannedStart) - PlannedEnd + 1)
how can i do it
Thanks a lot