[Zope-CMF] Skin

[TrashMan]

Good morning, i'm a newbie!

I don't understand the skins of CMF.

My portal structure  is 

Root MyPortal -> subdir A -> subdir B

I define the skin under portal_skin/custom/myskin
I set the skin in portal_skin properties  and then I set it as default
skin.
All is good. 
The problem is:
the subdir A must have another Skin! When I type
http://localhost/myportal/A the skin must not be the default skin but 
portal_skins/custom/myportal/A

Help!!! And...sorry for my bad english.

Max