Hi,
I have the following formula, it seems to work to the point that if the vlookup returns true then the 0 appears, but when false it will not pull through the value in cell N3.
=IF(OR(VLOOKUP(A6,'Summary Source'!$E:$E,1,FALSE)=A6,VLOOKUP(A6,'Summary Source'!$F:$F,1,FALSE)=A6),0,SUM(N3))...