I know this is the wrong way round... but

Is it possible to use AD in front of Samba for our PC clients, so that the user accounts are in Samba/Open LDAP.

Managing our fleet of Windows PC's is becoming more and more difficult with just Samba v3 - until Samba v4 comes along, it would be great if we could leverage Active Directory, but have the accounts stored in Samba/Open LDAP.

Windows PC's are a minority in our organisation & Samaba/Open LDAP are used for just about every service (Zimbra/RADIUS/Intranet/SAN/Printing/...) so it will have to remain the definitive account source. Anyway, it probably can't be done, but I thought I would ask for ideas anyway.