It is not allows the use of wildcards. if you run php in your server then you could list all files in the directory and generate sitemap.xml automatically using the DirectoryIterator .
// this is assume you have already a sitemap class.
$sitemap = new Sitemap;
// iterate the directory
foreach(new DirectoryIterator('/MyWebsiteName/DirName') as $directoryItem)
{
// Filter the item
if(!$directoryItem->isFile()) continue;
// New basic sitemap.
$url = new Sitemap_URL;
// Set arguments.
$url->set_loc(sprintf('/DirName/%1$s', $directoryItem->getBasename()))
->set_last_mod(1276800492)
->set_change_frequency('daily')
->set_priority(1);
// Add it to sitemap.
$sitemap->add($url);
}
// Render the output.
$response = $sitemap->render();
// Cache the output for 24 hours.
$cache->set('sitemap', $response, 86400);
// Output the sitemap.
echo $response;