Frogs have external fertilisation, so if your frogs have had any attempts at breeding, they have been unsuccessful.
When frogs breed, the male will very firmly grasp the female (like a piggy back ride, and he'll be holding on very tightly with his front legs). The female then goes to the water with the male riding on her back, and when they are in the water she releases her eggs and he releases sperm at the same time. It's not like in other animals where fertilisation is internal with the male inseminating the female and then her going on to lay fertile eggs or give birth at a later time.
Green Tree Frogs can have thousands of eggs, you'll see them in the water if they're successfully spawned. If you don't have a large enough body of water they won't ever spawn. If you do get eggs and don't want them, you will probably be able to find someone happy to take all the eggs off your hands.