Thanks to you folks, I'm now able to have a total in the main form that sum values from a subform. This part works fine.

But there's still a minor problem I can't solve: if the user delete a row with a value in it from the subform, the total is not updated. It seems logical, given that there's no "user input". 

So I tried to apply the same script on "on delete row" but nothing happens. Any idea ? 

Here is my script:

temp_total = 0.0;

for each x in FPA1

{

    if (x.Montant  !=  null)

    {

        temp_total = (temp_total  +  x.Montant);

    }

}

input.TFPA1 = temp_total.toLong();