I need to add a text field

I've been reading through forums and PHP, and I know it is possible, but I am not really finding what I need to actually accomplish the task. Any help would be appreciated. I need to add a "notes" field to the order update (shipping confirmation) page. I would like to be able to have the OPTION to add a note to the customer in the shipping confirmation email.

I am assuming this would involve adding a text field labeled Notes in the order update PHP page, but then I also will have to create the PHP command or require line in the email shipping confirmation template that would actually look for content in the update page, and if there is none, skip it, but if there is something, include it in the email. I am working on learning a lot more PHP, but I must admit I am not there yet...

OR, is there a built-in in the Powerstore 2 software that writes the code for me? I have Powerstore 2, and I am a subscriber to Web Assist...

Thanks,
Michelle