Using household products to deter cats from "going"?

My cat has been doing her business outside in some dirt right underneath my window! The smell gets inside and stinks up the house. I've already cleaned the area of "debris" and sprayed the dirt w/a household cleaner to discourage her from using that spot anymore...it didn't work. What can I put on the dirt that I might alredy have in my house(no expensive pet store stuff, please!) to keep her away from there?