You can setup standard quota system, comes with any standard linux distro and set appropriate permissions.
Please refer following link for setting up Quota.
http://www.linuxhomenetworking.com/w...ge_with_Quotas
Please note that for setting up quota, your shared samba folder should be on separate partition.
Quota can be applied only on partition, not on individual folders.
If still have doubts, please reply back.