ispCP Omega comes now with support for mod_cband.
This means that you can handle the complete Bandwidth(Speed, Traffic) for one or more Domains.

If you want to use it, you must enabled mod_cband

# a2enmod cband

You find now more Infos about it in the Apache ispcp.conf

# vi /etc/apache2/sites-enabled/ispcp.conf

Here is now the mod_cband content:

<IfModule mod_cband.c>
    <CBandUser yourdomain.tld>
         CBandUserLimit 1024Mi
         CBandUserScoreboard /var/www/scoreboards/yourdomain.tld
         CBandUserPeriod 4W
         CBandUserPeriodSlice 1W
         CBandUserExceededURL http://admin.ispcpdemo.homeip.net/errors/bw_exceeded.html
    </CBandUser>
</IfModule>

CBandUserScoreboard = File for writing down the bandwidth usages
CBandUserLimit 1024Mi = This is the max. Traffic for this User
CBandUserPeriod 4W = The Period is set to 4 Weeks
CBandUserPeriodSlice 1W = The Period is cut in 1 Weeks slices
CBandUserExceededURL = This is the Site that comes up when the Traffic is exceeded like this  http://img227.imageshack.us/my.php?image=cbandbj8.jpg

There are alot of more Options to handle IP´s or Search Engines like the Google Bot to slow down the Speed.

You can check the mod_cband status page here
->  http://yourdomain.tld/cband-stats
->  http://yourdomain.tld/cband-stats-me

Notes

By default in Debian the cband-stats and cband-stats-me are enabled. Both pages can be accessed by anyone meaning anyone is able to know who is visiting any page of the domain.

Make sure to at least disable cband-status-me because it provides some options to reset the bandwidth counters.