Recruit a friend to sit on your hips and hold a dumb bell or some plates, other wise the weight load isn't going to be on your calves if you hold the weights in your hands.
ASIMMER is right but I've never really like the sound of that:/ You can try doing them one leg at a time and that will put a little extra weight on your calf.
-------------- "Have you paid your dues?" - David Alan Coe