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