Don't rub your cat's nose in it! That's way beyond cruel and the cat will learn nothing apart from the owner is mean and deranged. Get a litter tray!! After all, humans have indoor loos, so why shouldn't a cat, and especially an old cat? Would you like to squat in the garden in the rain, winter? Most large pet places or Argos etc, sell a litter tray which is like an igloo with a removable lid and a filter which absorb smells. The pine woodchip litter is better at absorbing liquids and has a pleasant fragrance. One thing to note is that a lot of previously 'clean' cats do become a bit absent-minded with age and sometimes mess where previously they didn't. It comes to us all....