adding extra lines when in check out

here is my problem and question.

I run a custom invitations company. I want to have my customers click on the design, and add to cart. Once they have added to cart and are at check out, i want them to be able to write in what they want the invitation to say. Message, names of people that its going to, and extra comments.

I want this to happen when they are in the section selecting the shipping options, or if possible before it.

Is there a way to do this?

I use the single page checkout mod and so all my checkout page is contained in one page. There is a block on this final page called:

"Special Instructions or Order Comments"

Where customers can add text before clicking confirm.

It is possible to have as many of these boxes on that page as I want. Simply by copying and duplicating the block of code that generates this box in the tpl_checkout_split.php file used by this mod, I could have several such boxes if required.

It would then be straightforward to change the "Special Instructions or Order Comments" text to read "Please Enter Invitation Text" or whatever you want it to.

Just an idea, maybe there will be better ideas from others....

I had thought of that, but i wasn't sure if there is anything else that i can do with it.

Thanks though