interesting product situation

Hi guys,

I have one product of type membership that we allocate no weight to, even though we send out a membership pack. This is because the product has factored in the delivery costs. But other products have weight. However if they buy a membership and another product there is no need to charge the delivery costs for the other product because generally speaking the other product can be included in the delivery cost of the membership pack.

What might be a solution here so that we don't charge or so that we can waive the delivery costs when we need to for an order.

Thanks,

Mat