i am getting the above error when trying to run the following code

Dim Res1 As Integer
Res1 =
Worksheet.Evaluate("=sumproduct(--(am1:am30000=""=08/01/2009""),--(am1:am30000=""<09/01/2009""),(BN1:BN3000))")
MsgBox Res1

I am using excel 2007...