I just tried this and if I understand your need then this should work. NO guarantees but, here goes!
On the Orion server, bring up Report Writer. (Usually found in Start>All Programs>SW Orion>Report....>ReportWriter)
Select New from its menu bar.
When the new report comes up, enter the name for the report. (Choose one that says what interface group you want to refer to)
Select the Tab "Select Fields" and add a new field.
Select the Historical Interface Traffic>Transmit+Receive Data Combined>AverageRecv+Xmit bps
The function for the field should be Average.
Select the Filter Results tab
Change the Select "Records Where" entry to ANY
Add an elemetary condition for EACH interface you want to summarize.
The entries will be InterfaceID and IS EQUAL to and then the INTERFACE ID of each of the needed interfaces.
(You can get the interface ID number by simply going to the device and then hovering over the interface you want. At the bottom of your browser, the interface ID will appear. Use that number)
NEXT: Select the Time Frame tab and enter the criteria you wish to report on.
Select the Summarization Tab and make sure that Do NOT SUMMARIZE is checked.!!!Odd huh!
Select the Field Formatting Tab
Click on the one field you have defined. Change your Column Header to something meaningful to you.
In this case you should make sure that the format is bandwidth and the units are bps.
The Valid Range MUST be All Values.
Click on Execute Query and watch the magic.
Then click on Preview and then SAVE this mess with a good filename.
NOW you have the report.
If you want this on a Web page, let me know. I can tip you in that direction.
Regards,
One note on this. When saving the file you will receive an error about not having the Interface ID as a field. Simply disregard that message and continue the save. It still works.
Sorry for not including that info.