A variation on Ben's answer to use a windowing clause, which seems to take care of your updated requirements:
select eventno, eventtype, totalcharge, remainingqty, outqty,
initial_charge - case when running_outqty = 0 then 0
else (running_outqty / 100) * initial_charge end as remainingcharge
from (
select eventno, eventtype, totalcharge, remainingqty, outqty,
first_value(totalcharge) over (partition by null
order by eventno desc) as initial_charge,
sum(outqty) over (partition by null
order by eventno desc
rows between unbounded preceding and current row)
as running_outqty
from t42
);
Except it gives 19.2
instead of 12.8
for the third row, but that's what your formula suggests it should be:
EVENTNO EVENT TOTALCHARGE REMAININGQTY OUTQTY REMAININGCHARGE
---------- ----- ----------- ------------ ---------- ---------------
4 ACQ 32 100 0 32
3 OTHER 100 0 32
2 OUT 60 40 19.2
1 OUT 0 60 0
If I add another split so it goes from 60 to zero in two steps, with another non-OUT record in the mix too:
EVENTNO EVENT TOTALCHARGE REMAININGQTY OUTQTY REMAININGCHARGE
---------- ----- ----------- ------------ ---------- ---------------
6 ACQ 32 100 0 32
5 OTHER 100 0 32
4 OUT 60 40 19.2
3 OUT 30 30 9.6
2 OTHER 30 0 9.6
1 OUT 0 30 0
There's an assumption that the remaining quantity is consistent and you can effectively track a running total of what has gone before, but from the data you've shown that looks plausible. The inner query calculates that running total for each row, and the outer query does the calculation; that could be condensed but is hopefully clearer like this...