You could probably try something like the following. However be very wary of where you run this comman due to the "-f" option of the rm command.
cd destination_directory
rm -f `find * -mtime +30 | xargs ls -l | grep -v user1 | grep -v user2 | grep -v user3 | grep -v user4 | awk -F " " '{print $9}'`
jerardfjay