In order to get rid of the EXCEPT
you could combine the conditions and negate the second one:
SELECT DISTINCT
P.Name,
T.Training
FROM Prof AS P,
Training_done AS TC,
Trainings AS T
WHERE ((P.Name Like '*' & NameProf & '*') AND
(P.Primary_Area = T.Cod_Area))
AND NOT ((P.Name Like '*' & NameProf & '*') AND
(P.Cod_Prof = TC.Cod_Prof));