I have a workbook that i am trying to link to a closed workbook, and i am
getting an error message on the value. i know that sumproduct can be used
but am unfamiliar with it, can someone help me

my formula is

=SUMPRODUCT('Z:\PURCHASED PRODUCT 2007.08\[PURCHASED PRODUCT
2007.08.xls]ORANGE CONC HOWEY'!$K15:K9999,"<="&A7,'Z:\PURCHASED PRODUCT
2007.08\[PURCHASED PRODUCT 2007.08.xls]ORANGE CONC HOWEY'!$Z15:Z9999)

Thank you!