It is probably because your function cannot handle and return an array,
being single cell driven. Post the function and the criteria, we'll try and
help.

--

HTH

RP
(remove nothere from the email address if mailing direct)


"robot" wrote in message
...
I want to sum over cells in column A based on a criterion on column B. The
criteria is kind of complicated, and a custom function [Fn(S as string) as
byte] has been written for the purpose. The formula

= IF(Fn(B2)0, A2,0)

works fine, so I tried the array formula

{=SUM(IF(Fn(B2:B5)0, A2:A5,0))}

but that doesn¡¦t work. (returning a #VALUE! error)

Suggestions are most welcome!