Hi

I have to write a new shipping module, basically our shipping works like this:

each item has a shipping code (A, B, C etc) the customer pays the highest shipping code for what they order, so if they order 2 items with code B and 1 with code C, then they pay code C for the whole order.

Just to complicate things, we also ship to 4 different country bands, so I need different codes for each set of countries.

Can anyone point me in the right direction of how I do this please?