That hose is shot bro, it's not supposed to separate at the band, the upper radiator hose is a unit with three hoses attached to it. Click on the link below, it's part #1 in diagram, I replaced all of the cooling hoses and expansion tank on my 2002 4.6is last month, you are advised to do the same. And no you can't replace one hose at a time on these damn cars, it will put pressure on the older hoses and they will blow on after the other, ask how me and lots of others on this site know...lol!! I see you only have two posts, so obviously your new, use the search function and do some reading, again trust me, replace all the hoses, not just one!
http://www.realoem.com/bmw/showparts...55&hg=11&fg=35