Special discount option for groups

Hi, I use a creloaded b2b 6.4 shop, and i need yo to make some adjustments to the customer group-system. What i want to achieve is to be able to create groups and be able to define a discount in % that applies to member of this group and to definer if members of this group should pay shipping or not. This should work without interfering with the Customers Groups system. You should ensure that the modifications works throughout on the whole payment process. Please ask questions before bidding. Regards Søren