orders would be a distinctcount of order#field.
you can show the totals at any group level or the report total
back orders , if i understand you correctloy will need to use shared variables or running totals. YOu will need one per level you wnat to display it at.
here is the RT version (my preference)
right click on RT
select new
name=BackOrderTotal (or whatever)
field to summarize=order#
type=distinctcount
evalaute=use a formula
table.qytBO>0
reset=never (for report total)
place in report footer (RTs do not work in Headers
for group level totals do the eact same thing but change the reset to a group.