Using SUMPRODUCT and different variables

I’m currently using SUMPRODUCT to get the required result. I have a working formula with the correct results and now wish to add an extra search criteria.

My basis is this, which picks out all the content in Column P and adds up all those in the month of July:
=SUMPRODUCT(NOT(ISBLANK('[MS5]MS5'!P5:P1000))*(MONTH('[MS5]MS5'!P5:P1000)=7))

I now want to add the criteria into this where it only adds up based on B5:B1000 being equal to 1 (1 being a product code, rather than an actual number).

I believe this is simple, but for some reason it has stumped me today!