Array Formula Using the Sum Function

I am trying to get the JSum function to work on a simple spread sheet but it just wont work for me. Can anyone please help?

Eg:
It should only return data for one field but it's returning data for all North.

=SUM((B98:B106="Jan"),(C98:C106="North")*D98:D106)


Month Region Sales
Jan North 100
Jan South 200
Jan West 300
Feb North 150
Feb South 250
Feb West 350
Mar North 200
Mar South 300
Mar West 400

Try SUMPRODUCT, i.e.

=SUMPRODUCT((B98:B106="Jan")*(C98:C106="North"), D98:D106)

Thanks Daddylonglegs for your speedy response. I tried your suggestion but it returns a zero.

Does column B contain text or formatted dates? If they're dates then perhaps try

=SUMPRODUCT((MONTH(B98:B106)=1)*(C98:C106="North"), D98:D106)

or if column B is text try

=SUMPRODUCT((B98:B106="Jan")*(C98:C106="North")* D98:D106)