I was having trouble with a SumIf function to a linked file. I searched
the newsgroups and found an alternative using Sumproduct. In this
formula:

SUMPRODUCT(--($B$8:$B$800=1),'C:\MyDocs\[2005exp.xls]Sheet1'!$C$8:$C$800


what does the SUMPRODUCT(--( do? Why the double dashes?

Thanks