revesrse grn

hi,

here i want to make the setting such that no GRN not to be reversed when its MIRO is done.

ex. suppose IN PO QTY -20 VALUE -100.

IN MIGO QTY -10 VALUE - 50.

AGAINST ABOVE MIGO IN MIRO QTY-10 VALUE -50.

IN ABOVE EXAMPLE WHEN MIRO IS DONE OF QTY 10,THE SYSTEM NOT ALLOWED THEN TO REVERSE THE GRN BECAUSE THE BILL IS PAID TO THE VENDOR IN MIRO. SUGGEST ME FOR THAT.