The nature, gender and ability are determined when the egg is made and the IVs are set when you take it from the day care man. So if you save before taking the egg then you can SR for different IVs while keeping everything else the same.
For more information on breeding read the breeding guide in the articles section of the site: http://www.smogon.com/dp/articles/
For more information on breeding read the breeding guide in the articles section of the site: http://www.smogon.com/dp/articles/