Subdomain stockage

Hello all i've just installed Ckfinder in ckeditor and it work

But i 've got a little problem
I need to use ckfinder on a website http://www.domain.com
but the files must be stocked in a subdomain http://sub.domain.com

My config files : 'uploadURL' => "http://upload.domain.com/",
'uploadDir' => "http://upload.domain.com/",

'dirPerms' => 0777,
'filePerms' => 0777,

My entire folder is in 777CHMOD
Please help me