=SUMPRODUCT(--(A12:A100=M1),--(C2:C100=""), B2:B100)

--
HTH

Bob Phillips

"Andeb" wrote in message
...
Hi,

I'm a bit if a newbie....

How can I sum only those cells that match 2 criteria (the company name
cell
on the left of the $ figure to be added must = a reference cell AND the
date
cell on the right must be blank)

This is a simple(?) spreadsheet that allows me to select a specific
customer
and shows me the outstanding debt (ie the date cell is empty because they
didnt pay on x date)