Yahoo! Small Business Hosting. Block Directory index?

I have a plan with Yahoo for web hosting. so i wanted to block user to see my directory structure but because of my plan i cannot use .htaccess or any php.ini configuration. How should i do?
preferably I don't want to add a index.html or php in every sub dir
Update: Additional index pages: yes i know it's fast to create new index pages but i have some php functions that scans for files in the directories, so i have to insert new exceptions into the for cycle.
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