如何在ios 5.0之前将文档备份停止到icloud

I am doing one application.In that i am creating the .txt files in DocumentDirectory at runtime.But they will backup to icloud.SO now i want to stop the backup in before ios 5 versions.From ios 5 onwards we have option to stop the back up process.I want to store the files in documents and not back up in before 5.0 versions.I am doing one application.In that i am creatin