ikke en proof-løsning, men kan muligvis fungere for dig uden behov for at ændre datoværdier
select *,(select sum(t2.Debtor - t2.Creditor) from TBL_test t2 where (t2.rdate < t1.rdate) or (t2.rdate = t1.rdate and t2.ID <= t1.ID) ) as RT
from TBL_test t1
order by rdate,ID