As mentioned, too much calcium in the crickets' diet will shorten their life span and you'll end up with a bunch of dead bugs. It's best to either dust the crickets before feeding, or dust the salad (but only if your dragon reliably eats his salad). That way you're sure that your dragon is getting the supplements. Another option would be to mix the calcium in with juice, water, or a bit of baby food and give it via syringe.