The easiest way I can think of to do this would be to assign a custom property to all of the interfaces you want to include in your report. Then you'll create a new Historical - Interface Traffic report in report writer. Select the fields you want displayed in your report (i.e. node name, interface name, total bytes transmitted, etc.) and filter the results based on the custom property you assigned your interfaces. Set the time frame for the report to "This Month." You should be able to run this report throughout the month and see where you are on each of your interfaces.
Hope this helps!
I added a word to the description of the interfaces in question, and then filtered the report by that word. Works great. Now just need to find a way to alert if that value goes above a max. I think the same filtering method will work.