sumproduct with multiple criteria

I have a problem with my formula. I tried using sumproduct formula for my database but it resulted to #VALUE!

heres the formula:

=SUMPRODUCT(('[BB Voucher.xls]ACCOUNTS PAYABLE VOUCHER'!$O$8:$CA$5000)*('BB Voucher.xls'!APVACCTCREDIT=$BA6)*('BB Voucher.xls'!APVDATE>=FIRSDATE)*('BB Voucher.xls'!APVDATE<=ENDDATE))

what i want to get is the sum for each account number from row 5 at each change in specific month in column C in another worksheet wherein the account number is listed in column A.

Can anyone please help me?

Thanks in advance...

thanks... i figured it out...