Hi Martin,
no it's not about excluding pages.
I am working on a part of a larger site and I'd just like to see my changes to be crawled as fast as possible, that's all. For that reason I thought about submitting a sitemap just for that part (doing it for the whole site is too time consuming at the moment).
But I just wondered if it's possible. If not I just wait until Googlebot has done crawling the new pages.