Delivery charge to customers postcode (per mile)

A delivery charge that works the total delivery from the user's own postcode (that can be set) to the customers postcode with an option to set how much per mile you will be charging. This would be ideal for company's that use their own transport to delivery larger items/orders and need a more accurate delivery price for the customer (with out adding thousands of delivery options). It would also be handy to also have an option to set a minimum delivery charge that would automatically be used if the customer was only a couple of miles away but you need, lets say, at least £25.00 to send a van out