change invoice price/quantity variance calculation logic

Summary:

for PO matched invoice,when (unit price of invoice line* quantity of invoice line)>=(unit price of receipt* quantity of receipt), is it feasible to change "Accrual" accouting class calculation logic to (unit price of receipt* quantity of receipt) and create a new accounting class to calculate amount =(unit price of invoice line* quantity of invoice line)-(unit price of receipt* quantity of receipt) ;

and when (unit price of invoice line* quantity of invoice line)<(unit price of receipt* quantity of receipt), change "Accrual" calculation logic to (unit price of invoice line* quantity of invoice line)-2*(unit price of receipt* quantity of receipt).