Dutch:
=SOMPRODUCT(ALS(E3:E21="Mark";B3:B21;"");ALS(E3:E2 1="Mark";C3:C21;""))

English (?):
=SUMPRODUCT(IF(E3:E21="Mark";B3:B21;"");IF(E3:E21= "Mark";C3:C21;""))

When I examine this function in the "function wizard" (pressing the fx
button), the wizard shows the correct value. When executing the
function in the sheet itself it shows #VALUE! (or whatever it is in
English) as not being able to calculate the formula. It shows me that
evaluating E3:E21 leads to an error.

What is wrong here ? How can it show the correct result in the wizard
but not in the sheet ?

Thanks for any help.