How could I perform different actions to different URL's.

For examle I want to download a parts of site of such structure:
www.site.net/part1.htm
www.site.net/part1/f1.htm
www.site.net/part1/f2.htm
www.site.net/part1/f3.htm
www.site.net/part2.htm
www.site.net/part2/f1.htm
www.site.net/part2/f2.htm
www.site.net/part2/f3.htm

Just even if i try to download www.site.net/part1/index.htm that redirects to
www.site.net/part1.htm it downloads part 2 too.