Custom Shipping Calculator in Checkout

Hi all,

We currently run a very basic store in which postage varies by item and postcode. At this stage, a customer buys an item and we send back an invoice with the postage charge based on what they ordered and where it will be delivered.

 

We want to stay away from the flat shipping rates or including postage in the overall cost. This often blows out and reduces profitability. However, sending invoices to customers is quite manual.

 

Has anyone come across a shipping calculator that follows the customer through the checkout process and completes everything in one hit? We can have a shipping calculator on our product pages but there is still a need to update and send back an invoice.

 

Thanks