Wouldn't that be wonderful if we could control such a bodily function!! I put a sheet or towels on the back of my couch/chair to protect it. I also put newspaper on my floor where Ana Grey perches or on the table where she perches. If she sits on me I put a towel on my knee/lap/shoulder. I can recognize when Ana Grey is going to go, a little wiggle of her tail, and am considering training her to go on a certain perch/place. There are members who have trained their greys to go at a certain place, perhaps some of those posts can help you.