Samba, can linux group permissions be determined based on user's workgroup

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http://askubuntu.com – Running Samba on Ubuntu Server. I have a share that is accessible to anyone on the network. The shared directory is set to 775. I want Windows users that are joined to a particular workgroup to get group permissions, in this case 7, while everyone else get's global permissions, in this case 5. Is this possible? (HowTos)