Have you tried newspaper or pee pads? One important tip is to not let them watch you clean it up, because it will enforce the behavior. Also get a pet-odor neutralizing spray from petsmart and cover your stairs with it, they like to go in the same spot all the time so she'll return to the stairs since she can still smell it there.
__________________  Sgt. Pepper, AKA "Sarge" & his mommy, Lacey.  |