I'm struggling with what may be a very simple issue: We plan to sell cat litter online throughout South Africa's 9 provinces, however, initially we want to limit delivery to selected major centers via courier. I would like to set up the checkout process as follows: 1. The customer must select his province and town from a drop-down, before he fills in the shipping particulars. If his town isn't featured we can not yet supply him; 2. Our courier offers A2 shipping bags. I can fit two cat litter bags in one A2 shipping bag, shipping costs therefore also need to be broken down as follows: 1 bag - RX, 2 bags = RY, 3 bags = RY, 4 bags = free shipping. I've tried some of the shipping plugins but they seem to link the shipping rate to the customer's address particulars in the shipping form. I want the customer to know if we ship to him before he wastes his time filling in the shipping form. Many thanks in advance.