Make a CalcField SignedTranQty with expression
(case
when PartTran.TranType IN ('STK-ASM', 'STK-CUS', 'STK-INS', 'STK-KIT', 'STK-FAM', 'STK-MTL', 'STK-PLT', 'STK-STK', 'STK-UKN', 'STK-DMR') then -1
when PartTran.TranType IN ('ADJ-CST', 'ADJ-QTY', 'AST-STK', 'DMR-STK', 'INS-STK', 'MFG-STK', 'PLT-STK', 'PUR-STK', 'STK-STK', 'SVG-STK') then 1
else 0
end) * PartTran.TranQty
Then another Calc field RunningQOH with the expression
SUM(SignedTranQty) OVER (Order By PartTran.TranNum)
Edit
You don’t need to select the GroupBy box on the other fields like you would with a plain SUM() function.