Printers and permissions

[AtSyber]

Hello

I've done a samba2.2.1a server, all is right. However, when I build a
printer share and want set some permission like 
valid users = toto @mygroup
have no effect.
But when I use a W2ksp2 with a admin login to set permission on this
printer share, that's work and stored !
So where are stored groups and users permissions ?
And how do it with the samba config file ?

Thank you for your help

Sylvain