Tweaking an integrated PHP calendar solution in a Cart

I installed a PHP multi-calendar solution ([login to view URL]) on a smarty PHP based shopping cart solution. This calendar is just for the buyer to give us an idea on what date and what time slots he would like to use to book the product of the service. The order price will still be calculated by the hopping cart original values, meaning price, quantity, options, etc… All I want is to add a step in the Cart page and the Checkout page so that the date and time information selected by the user be displayed and "posted" so that it's recorded in the Order details. Write me and I'll send you more details about the calendar script files and the shopping cart files.