You have conflicting conditions:

IF($B$1:$B$2000=""
IF($B9=$B$1:$B$2000

Unless B9 is empty, in which case those expressions would be redundant,
those expressions can't be TRUE at the same time.

The VLOOKUP/INDEX can be expressed in a SUMPRODUCT function as:

--(ISNUMBER(MATCH(C1:C2000,'[Lookupfile.xls]Name'!$A$1:$A$2000,0))),
--('[Lookupfile.xls]Name'!$B$1:$B$2000=$B9)

But, you have to straighten out those IF(B1....... things!

Biff

"Crazy Pete" <Crazy wrote in message
...
Within the attached array formula, I need to either perform a lookup, or
use
the data I have per iteration, to count for various values in column B.
However, as I understand, VLOOKUP requires a single value or reference as
the
lookup_value. I have tried using the INDEX function (see below), but it
appears to only pick up row 1 for each iteration, hence not matching with
any
valid lookup values.

How do I, inside an array calculation, specify the row which has been
found
to match the preceding IF statements?

Effectively, I wish to perform a lookup on another workbook, using column
C
and the row which has been found to match the two preceding IF statements.

=SUM(IF($A$1:$A$2000="OMS",IF($B$1:$B$2000="",IF(V LOOKUP(INDEX($A$1:$C$2000,ROW($1:$2000),3),'[Lookupfile.xls]Name'!$A$1:$B$2000,2,FALSE)=$B9,1,0),IF($B9=$B$1:$ B$2000,1,0)),0))

regards,
Pete.