DNS attribute per group

[Tomride]

I'm a newbie in freeradius, I have a production freeradius server connected with ldap directory, currently I'm assigning dns attribute(primary and secondary) in post-auth, the same servers for every user , It works fine but we need now to assign different dns server depending of their group. (O=). We don't know if check it in ldap or using groups in SQL.(radusergroup) , any idea?

Thanks in advance

Martin