Allow user to execute "repquota -g /"

[Luigi Cirillo <appost2@gmail.com>]

Hello, I need to allow an user to execute "repquota -g /" from a
script without superuser permissions on debian Wheezy. The user cannot
access to the file //aquota.group so I tried to create a group
"quotarep" but the root cannot chown the file:
##############################
chown root:quotarep //aquota.group
chown: changing ownership of `//aquota.group': Operation not permitted
###############################

I thinking to deploy a cron job to export the result of "repquota -g
/" on a file but I don't think it is a good way.
Do you know how I can solve this?
Thank you