Need to tweak the export function

Hi,

with the export function in /wp-admin/includes/export.php , i need to do some things:

– how to generate a xml file automatically with cron, in a specific directory?

– i want to export only posts of a particular category, how to do that? the function is:

<?php if ($post_ids) {
		global $wp_query;
		$wp_query->in_the_loop = true;  // Fake being in the loop.
		// fetch 20 posts at a time rather than loading the entire table into memory
		while ( $next_posts = array_splice($post_ids, 0, 20) ) {
			$where = "WHERE ID IN (".join(',', $next_posts).")";
			$posts = $wpdb->get_results("SELECT * FROM $wpdb->posts $where ORDER BY post_date_gmt ASC");
				foreach ($posts as $post) {
			// Don't export revisions.  They bloat the export.
			if ( 'revision' == $post->post_type )
				continue;
			setup_postdata($post); ?>

bye ??