The following formula calculates correctly on my work PC, but not on
my home PC. Do you know the reason behind this? What can I do to fix
it? Any help will be much appreciated.

=IF(COUNTIF('Cash Flows'!$C$2:$C$50000,$A1)=0,0,
(SUMPRODUCT((MAX(('Cash Flows'!$A$2:$A$50000)*('Cash Flows'!$C$2:$C
$50000=$A1))))-SUMPRODUCT(SMALL(('Cash Flows'!$A$2:$A$50000)*('Cash
Flows'!$C$2:$C$50000=$A1),(COUNTIF('Cash Flows'!$C$2:$C$50000,"<"&
$A1)+1)-COUNTIF('Cash Flows'!$C$2:$C$50000,$A1))))+1)

Kevin