one way is to make two Running Totals (rt)
rt1
RT name=OrderRT
field to sumamrize=tableorders
type=sum
evaluate=on change of field - use table.item
reset=on change of field - use table.item
rt2
name=DeliveredRt
field to sumamrize=table.Delivered
type=sum
evaluate=for each record
reset=on change of field - use table.item
for your 'Outstanding' make a formula as
{#OrderRT}-{#DeliveredRt}
for your status make a formula as
if {#OrderRT}-{#DeliveredRt}=0 then then 'Complete' else 'Not Complete'