submit additional form on confirm page

i have a client, for whom I have created some complex shipping calculations, based on a combination of cart weight and shipping zip code.

this all works well, but now the client wants to display the shipping prices in a form, during the checkout process.

I don't think its a good idea to add another page to the checkout process, so the most logical place to put this form is at the top of the confirm.php page.

At this point, I know the cart weight and the shipping destination, the customer having already completed their shipping and billing details.

By default, the shipping method is ground, and i have the form displaying the shipping prices and expected delivery dates for all methods of shipping.

i would like the customer to be able to choose another method of shipping (if desired), - the option is stored as a session variable - and reload the page, which will update the shipping line in the eCart object.

the problem I have, is that when the form is submitted, it redirects to the checkout_success page, as if the confirm order button was pressend