I haven’t documented the local template functionality of the reports, @Blake, but you may be able to implement this on your own. When you first run a report, the scripts download a report “template” and hide it in your spreadsheet. (You can unhide it just like any other sheet.) There is a block where the data will populate (that you can’t modify), but you can add/modify the header, footer, and sides of the block. With a little creativity on placing the calculating cell and specifying range (and possibly dividing to account for sum rows) this could be a local mod to the report template that persists for future report executions.
Hope this all makes sense.
Randy