How do i get my cat to quit 'going' where the cat box USED TO be?

Our cat box USED TO BE in a little storage room that is now being remodeled for a guest bathroom. Paris, ( my cat ) keeps going in there and doing #2...It's disgusting to say the least. I want to know if there is anything that I can treat the bare plywood with that will make her want to go outside or down to the basement & also not hurt the wood... Help please!!??