Simple input-output function problem

Hi,

I have some trouble with this function. I'm trying to make an order function, where i input ordernumber(BestNr), productnumber(varenr) and amount(antal), which should return the product(varebetegnelse) and total price(pris) to BestNr.

function[varebetegnelse,pris]=Bestil(BestNr,varenr,antal)

    obj.ordrer(varenr).varer=[obj.ordrer(varenr).varer,varenr];
    obj.ordrer(varenr).antal=[obj.ordrer(varenr).antal,antal];

    varebetegnelse=obj.varebetegnelser(varenr);
    pris=antal.*obj.stykpris(varenr);

end

What am i doing wrong?