Other option could be to create Associative Array with Products as keys and Product Codes in a list as values and then fill new column with that. This requires JMP16 due to For Each, but it can be replaced with For-loop if necessary
Names Default To Here(1);
dt = Current Data Table();
aa = Associative Array(:Product << get values);
For Each({{key, value}}, aa,
aa[key] = dt[Loc(dt[0, "Product"], key), "Product Code"];
);
dt << New Column("Product Code Range", Character, Nominal, << Set Each Value(
Concat Items(aa[:Product], "/");
));
-Jarmo