I know this is not a normal setup but due to limited resources we are having to make the following scenario work :-)
We have a network share where access is controlled by security group rather than username. (Server 2k8 r2 domain - windows 7 enterprise clients)
Users (pupils)have a folder within that folder to save their work to. All pupils are a member of the required security group. Because of they way we are having to use this share users need to be able to modify but not delete files and folders so modify was granted and then advanced options were used to remove allow delete and delete subfolders and files (Permissions are inherited from parent folder).
This is working apart from when a user saves they get an error you don't have permissions to modify files in this location. Contact the administrator per permission to make these...