I have made many individual page changes to my priorities and change frequencies for my website pages so they are not all the same as the default settings. Since then I have added more pages and deleted others. How can I rerun the sitemapper and keep the priority and frequency settings I have in my current sitemap and just add in the new pages and delete the old ones. I do not want to have to reset all the priorities each time I rerun the sitemap. Can this be done?