Suppose I have in A1:A3 the values 1;2;10 and in B1:B3 the values "a";"a";"b" 
and in B5:B7 the values "a";"b";"c".
Then put in A5:A7 the array formula 
A5 {=SUM(IF($B$1:$B$3=B5;$A$1:$A$3;0))}
A6 {=SUM(IF($B$1:$B$3=B6;$A$1:$A$3;0))}
A7 {=SUM(IF($B$1:$B$3=B7;$A$1:$A$3;0))}
With MS-XL I get in A5:A7 the values 3;10;0, that is the sum of 1+2 for "a", 10 
for "b" and 0 for "c". With the OpenOffice Spreadsheet, instead, I get Err:504.
I know I could use the SUMIF() function, but:
1. First, I have many sheets using {SUM(IF(...))}
2. Secondly, the {FUNCTION(IF(...))} form is of much more general use and much 
more versatile than using the SUMIF(): e.g. I can do thinks like {MAX(IF(...))} 
or {AVG(IF(...))} and so forth...

Many thanx in advance & remember you all have my respect for your effort in 
this project :-)

Rob