I am not familiar with the SUMPRODUCT function. I asked someone to do some
work for me on a spreadsheet and he added the following expression to a cell:

=SUMPRODUCT(--('PO Log'!$AB$2:$AB$1203='Summary by Line Equivalent'!A2),('PO
Log'!$I$2:$I$1203),--('PO Log'!$AA$2:$AA$1203<"CANCELLED"),--(PO
Log'!$X$2:$X$1203<""))

I've been trying to understand exactly what this is doing, and I can't seem
to find anything that helps me understand what the "--" is for. Can someone
put this expression into English for me ?

Thanks !