eCart checkout - adding a textarea filed

I am trying to add a text area field to the checkout page for eCart. I found this tutorial:

http://www.webassist.com/tutorials/Add-a-form-field-to-your-existing-web-form

and I've followed the instructions (with the only difference being the type of form element and the name). Got the form field in place. Setup up the Binding and put the hidden field in the pp_confirm.php file to set the Session variable. Problem is, I still don't get a value when I display the Session variables after submitting the page.

What I want is to have a field where a customer can enter instructions about their order and have this print as part of the email receipt that goes to the customer and to the business.