Sum values from related app if two categories are iqual to...

Hello! i´m kind of new in podio but i have several apps design with some calculation fields with JS.

My problem:

APP A:

Mes (related field from APP B)

Date

Movimiento (category Field)

Caja (Category Field)

Monto (Money field)

Other fields

APP B: (kind of estadistic app)

Mes

Calculation Fields => this is what i want to solve...

I need to sum "Monto" field, if the item has selected some category fields (Eg. Tipo = "Ingreso" and Caja = "Marcos" both at the same time). Following some of the advices of Rainer (user) i get to this code:

var monto = @All of Monto;
var tipo = @All of Tipo;
var caja = @All of Caja;
var total = 0; for(var i=0; i< monto.length; i++){
if(tipo[i] == "Ingreso" && caja[i] == "Marcos"){
total += monto[i];
}
};
total || 0

With some items works great but some times it gives me bad results...

Any help please??

Thanks in advance!