If as implied you are using XL2007 then you should be using SUMIFS rather than SUMPRODUCT - the latter is inefficient:
=SUM(SUMIFS(DXB!G3:G3000,DXB!A3:A3000,{"PM","NM"},DXB!C3:C3000,1))
In SUMPRODUCT terms, either:
=SUMPRODUCT(--ISNUMBER(MATCH(DXB!A3:A3000,{"PM","NM"},0)),--(DXB!C3:C3000=1),DXB!G3:G3000)
or
=SUMPRODUCT((DXB!A3:A3000="PM")+(DXB!A3:A3000="NM"),--(DXB!C3:C3000=1),DXB!G3:G3000)
or
=SUMPRODUCT((DXB!A3:A3000={"PM","NM"})*(DXB!C3:C3000=1)*DXB!G3:G3000)
I prefer the first option in terms of flexibility.
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