I know you said you had steps but would you consider trying a ramp instead? Here's a cheap DIY for one to try out. If it doesn't work, no big deal.
http://www.yorkietalk.com/forums/gen...d-jumpers.html
As I said in other threads, Zoey wouldn't even go near the steps and Magnus would use it to go up but jump down. But after I placed the ramp, both use it to go up/down now.