class DepartmentPeople(models.Model):
    person = models.ForeignKey(Person, verbose_name=_('Person'), help_text
        =_('Person is a member of this deparment.'))
department = models.ForeignKey(Department, verbose_name=_('Department'),
    help_text=_('Pseron is a member of this department.'))
order = models.IntegerField(verbose_name=_('Order'), help_text=_(
    'What order to display this person within the department.'),
    max_length=255)


class Meta:
    verbose_name = _('Department Person')
verbose_name_plural = _('Department People')
ordering = ['order']

def __unicode__(self):
    return (self.person.first_name + ' ' + self.person.last_name +
        ' is a member of ' + self.department.name + ' in position %d' %
        self.order)
Define an order for ManyToManyField with django