I have the following formula in my worksheet but I'm getting a "#Value!"
error. Can anyone shed some light if there is a problem with my formula? When
my value in B3 is false it works fine but when it's true I get the error
message above.

=IF($B$3="",SUMPRODUCT(--(MONTH(Detail!$I$2:$I$43998)=MONTH($A7)),--(YEAR(Detail!$I$2:$I$43998)=YEAR($A7)),--(Detail!$B$2:$B$43998)),SUMPRODUCT(--(MONTH(Detail!$I$2:$I$43998)=MONTH($A7)),--(YEAR(Detail!$I$2:$I$43998)=YEAR($A7)),--(Detail!$B$2:$B$43998=Summary!$B$3)))