on the checkout page, add a select list to select the shipping service:
<select name="UPS_Service" id="UPS_Service">
<option value="01">Next Day Air</option>
<option value="03" selected>Ground</option>
</select>
on the confirm page, locate the other hidden form element, and add a new one to capture the value posted from the checkout page:
<input name="UPS_Service" type="hidden" id="UPS_Service" value="<?php echo((isset($_POST["UPS_Service"]))?$_POST["UPS_Service"]:"") ?>" />
on the confirm page, you now need to store the selected shipping service in a session variable. Go to the server behaviors panel and click the plus button
Select eCart -> General -> Set Session Value.
for the trigger select any for post.
set the name to "UPS_Service"
for the value, click the lightning bolt and select the "UPS_Service" form element.
In the list of server behaviors, double click the UPS Shipping server behavior.
For the Service type, click the lightning bolt and select the "UPS_Service" session variable.