MATCH A CR/DR MEMO TO AN INVOICE WITH A PO

I cannot validate/approve an AP invoice due to: 88 items invoiced @ $37.41 each = $ 3292.08 The Purchasing Manager GOODS RECEIVED a qty of 88. The Purchasing Manager later REJECTED a qty of 4. The GOODS RECEIVED qty has now changed to a qty of 84 in the 'match to purchase orders' window. I have now received CREDIT MEMO from the supplier for the 4 rejected items (4 @ $37.41 each = $(149.64) How can I validate/approve the original invoice if the QTY RECEIVED does not equal the QUANTITY INVOICED?