=SUMPRODUCT('[workbook name.xls]sheet name'!$A$2:$A$8="value",'[workbook
name]sheet name'!$C$2:$C$8)

--
HTH

Bob

(there's no email, no snail mail, but somewhere should be gmail in my addy)

"Xueling" wrote in message
...
When using 'sumif' formula, if the data i am suming is in another file, i
will get error msg if i do not open the 2 files at the same time.

Is there another function i can use that would allow me to acheive the
same
result without using 'sumif'?

i tried 'vlookup' but it does not add up.

Thanks so much!