Do you mean you want to get the group permissions on a specified file, and then set the permissions on all other files (recursively) to that value? What have you tried so far?
I'm running a duel boot/partition machine with Ubuntu 12.04 and Windows 7. On Ubuntu OS, I wanted to change the permissions in one of my directories so could extract files into that directory. In the terminal I entered chmod -R 777 /usr/share/icons which gives the owner, group, global read, write, and execute permissions.