AVG complex agrr or if

[Anonymous]

Hi all,

My table is like that and

I want to calculate the average of marge but

        I want to take all the value marge if  Début de contrat <31/08/208 and date fin contrat is empty or > 31/08/2018

       I Don't want to take the value marge if date fin contrat <31/08/2018 and if Matricule facturation = INTERNE.

Thanks for your help