It sounds like you will need a different list that is just the brands and not the products. You would then need to use unverified perl to add the items from that new list based on the response to Q3. So in the example below, if item 1 or item 2 is selected I'm adding the first item from your 'newlist' which would be M&Ms. Then if item 3 is selected I'm adding item 2 which is the next brand. And so on...
Begin Unverified Perl
if (VALUE("Q3_1")==1 || VALUE("Q3_2")==1)
{ADD("NewList",1);}
if (VALUE("Q3_3")==1)
{ADD("NewList",2);}
if (VALUE("Q3_4")==1)
{ADD("NewList",3);}
End Unverified