Excel 2007 : Sumproduct Help

[emmarky]

I have been using the following formula to calculate a 4 year running programme and it works fine. The trouble i have is when i try to use sumproduct to make this formula myself i get the wrong formula so i am having to copy and paste the correct one from a spreadsheet that works.

The formula i need and use is
=SUMPRODUCT(--('Site Listing'!$B$1:$B$600="TESCO EXPRESS"),--('Site Listing'!$K$1:$K$600="CLEAN ONLY"),'Site Listing'!$L$1:$L$600)

The formula i creat when trying to use excell is
=SUMPRODUCT('Site Listing'!B1:B600="TESCO EXPRESS",'Site Listing'!K1:K600="CLEAN ONLY",'Site Listing'!L1:L600)

I can clearly see what is missing from the formula but cannot figure out what step or where i am going wrong by using excell to create it??