Answer #1: Why not try a light dusting of chilli powder
-- Dave E. Comment
Answer #2: The website of the Feline Health section of the Vetinary department of Cornell University has a brochure on "House Soiling" by cats which gives good advice and analysis the reasons for the problem; it can be stress and trauma, an infection or an a combination. The person whose bed, or side of the bed is also significant. A 'Must Read article. Link to Article -- qznaz Comment