If you haven't read it already, take a look at the doc for this feature,
http://vicidial.org/docs/ALTERNATE_NUMBER_DIALING.txtAs for stopping dialing for an account, take a look at the agc/deactivate_lead.php script:
# This script is designed to be used in the "Dispo URL" field of a campaign
# or in-group. It should take in the campaign_id to check for the same source_id
# in order to change it's status to whatever duplicate_status is set to. The
# sale_status field is a list of statuses separated by three dashes each '---'
# which contain the statuses for which the process should be run.
#
# This script is part of the API group and any modifications of data are
# logged to the vicidial_api_log table.
#
# This script limits the number of altered leads to 100 per instance and it will
# not run if the search field of the lead is empty.
#
http://server/agc/deactivate_lead.php?s ... _to_file=1#
# Example of what to put in the Dispo URL field:
#
VARhttp://192.168.1.1/agc/deactivate_le ... _to_file=1#
VARhttp://192.168.1.1/agc/deactivate_le ... _to_file=1