I have an object with field state (draft and done), and field compteur, i want to increment compteur until the the field change the state to done,

The problem is when i valid the state, the field compteur become zero, and i want to stay in last value

this is my code :

def my_function(self, cr, uid, ids, field_name, arg, context):
    res = {}
    for cons in self.browse(cr, uid, ids, context=context):
        if cons.state == 'draft' :
                compteur_mtn = 0
        date_creation_repertoire= cons.date_creation_repertoire
        date_mtn= time.strftime('%Y-%m-%d')
        date_creation_repertoire = date_creation_repertoire.split('-')
        date_mtn= date_mtn.split('-')
        jours1 = 0
        jours2 = 0
        jours1 = ((int(date_mtn[0]) * 365) + (int(date_mtn[1]) * 30) + int((date_mtn[2])))
        print jours1
        jours2 = ((int(date_creation_repertoire[0]) * 365) + (int(date_creation_repertoire[1]) * 30) + int((date_creation_repertoire[2])))
        print jours2
        compteur = (jours1 - jours2)
        print compteur
        res[cons.id] = compteur
        else : 
        res[cons.id] = False
    return res



    'compteur': fields.function(my_function, type="float", string='Délai en j'),