I have the impression that you want something like:

=SUMPRODUCT(SUMIF(INDEX(DataRLambda,0,1),$F$15:$F$ 19,INDEX(DataRLambda,0,2)))

You can eliminate INDEX() for more speed by substituting the appropriate
ranges instead of using DataRLambda...

Lets say that DataRLambda refers to A2:D20. The SumProduct formula would
become:

=SUMPRODUCT(SUMIF($A$2:$A$20,$F$15:$F$19,$B$2:$B$2 0))

Replace comma's with semi-colons for your version of Excel.

BartDesc wrote:
It seemed simple:
={SUM(VLOOKUP((F15:F19);DataRLambda;2;FALSE))}
should work, but doesn't. F15 is used every time for evaluation in VLOOKUP.
I have some experience in excel so I don't think it's any obvious mistake.
My conclusion is that using Vlookup in a formula array doesn't work.
Can anybody second that?
Did anybody find an elagant workaround? (I could create extra calculations
in extra columns or even some VBA programming).

Thanks,
Bart


--

[1] The SumProduct function should implicitly coerce the truth values to
their Excel numeric equivalents.
[2] The lookup functions should have an optional argument for the return
value, defaulting to #N/A in its absence.