Add 'Create an invoice' to our Big Commerce Site -- 3

This has to work within Big Commerce. Please don't bid if you are not familiar with Big Commerce web sites. You do not have access to the SQL or PHP. It would need to be accomplished within the template file area. We allow customers to on our site to request a shipping quote instead of going with the calculated quote the site generates. We would like to create an invoice for the customer for that shipping quote within our site, that we could then send the customer a link to pay for the shipping. Currently we create an item in inventory for $0.00 and add the shipping amount and have them purchase that, but it is a very Clunky way to accomplish this. We would like the link to take the customer directly to the cart screen with a bill for just the shipping amount we specify.