Custon XML sitemap

I need a script that converts an extremely large text file list of keywords into a [login to view URL] file, using the correct google xml sitemap format. The features I need are below: 1)The ability to select and read from multiple text files of keywords so i dont have to combine them into one myslef. 2)Multiple threads, the maximum according to your experience a computer can handle becasue the text file is so large. I want this task to be finished as fast as possible. 3)After each 50,000 keywords, a new sitemap file should be created. example [login to view URL] [login to view URL] [login to view URL], and so on until job is complete. In the script, I would like to have the features below. 1)last modification date and time 2)I should be able to type the URL i want to use. example is : [login to view URL] 3)input file(s), 4)Output here is an example of the input keyword text file below: keyword1 Key word 2 key WORD3 keyWORD 4 here is an example of how the finished output [login to view URL] should look is below: <?xml version="1.0" encoding="UTF-8"?> <urlset xmlns="[login to view URL]"> <url> <loc>[login to view URL]</loc> <lastmod>2011-01-27T23:55:42+01:00</lastmod> <changefreq>daily</changefreq> <priority>0.5</priority> </url> <url> <loc>[login to view URL] word 2</loc> <lastmod>2011-01-27T23:55:42+01:00</lastmod> <changefreq>daily</changefreq> <priority>0.5</priority> </url> <url> <loc>[login to view URL] WORD3</loc> <lastmod>2011-01-27T23:55:42+01:00</lastmod> <changefreq>daily</changefreq> <priority>0.5</priority> </url> <url> <loc>[login to view URL] 4</loc> <lastmod>2011-01-27T23:55:42+01:00</lastmod> <changefreq>daily</changefreq> <priority>0.5</priority> </url> </urlset> ------ send me a private messege for more details.