The only way I stopped it was when I was looking for a house I looked for something that had a small room I could use for just the cats(cat room). I have two litter boxes in the closet which has sliding doors. The dogs never have access to it. I couldn't keep them out of the litter boxes before.
Misty- Samoyed Mix, Tannor- Golden Retriever CGC
Robyn- GSD CGC, TC, Midnite-GSD CGC,TC, Brennan-Golden Retriever CGC, Batman-Husky/Greyhound , Apollo-GSD