netting the open quantity
I have PO quantity(EKPO-MENGE) and goods receipt quantity(MSEG-ERFMG). Here i want to calculate the open PO quantity which is EKPO-MENGE - MSEG-ERFMG .But here if multiple material docements r getting created for the same for one PO and partial goods receipt quantity is done thru these multiple material documents. then how to net the open quantity.
For example :
PO no PO quantity material documents GR quantity
10 10 100 1
Now i need the open quantity as 9
Even i tried with At new Ebeln.but i am not getting it.
Can anybody help me in this.