[Samba] question regarding samba permissions

[skull]

I want to make a subfolder read only for certain users.
for example: /data/pool is public rwx for all users. 
and now i would like to make a /data/pool/subfolder only rwx for user1 and grant read only permissions to user2 and user3
how do i do this? any links or direct tips on that?

my suggestion would be something like this, but as you can imagine it didn't work:

# The general datapool where everyone may rwx
[pool]
    comment = Datapool
    path = /data/pool
    force directory mode = 700
    force create mode = 770
    create mode = 770
    directory mode = 770
    public = yes
    writable = yes
    printable = no
    valid users = user1 user2 user3

#My new Protected Subfolder
[Write Protected Subfolder]
    comment = Write Protected Subfolder
    path = /data/pool/subfolder
    force directory mode = 700
    force create mode = 770
    create mode = 770
    directory mode = 770
    public = yes
    writable = yes
    printable = no
    valid users = user1