Disable create subdirectory Solaris 8 ftp

Running Solaris 10. For FTP users or groups, I want to prevent them from creating new subdirectories, but I still want to allow them to create, upload, download files from the subdirs.

I understand how to set the general file/directory permissions -- read, write, execute. So for a directory, I'm looking for a way to set the permissions as execute, so that the user can access the dir, and read/write files in the dir, but is not allowed to create directories within the dir.

Thanks for the help!