We calculate the energy of excitons in parabolic quantum wells using the effective variational Hamiltonian (EVH) method which allows us to find all energy levels of the exciton by searching for solutions within a very broad class of trial functions whose form is also subject to variation. We use the new method to find the exciton binding energy of 1s, 2s and 3s states of an exciton formed below the ground electron and hole subbands in parabolic quantum wells made of (Ga, Al)As and (Cd, Mn)Te. We calculate also the binding energies of excitons formed between excited quantum well levels. The calculations are performed for various values of an external magnetic field parallel to the growth axis of the heterostructure.