Thanks for the kind comment!
As long as the client provides the first name on page 1 it should be passed through the hidden form element on page 2 to ListMail without generating an error. Since when ListMail shows an error it might be required to go back -two- pages, you might also want to add a JavaScript check on page 1 to make sure the user has entered something.
<form method=post action=/path/to/page2.php onSubmit="if(!document.getElementById('fn').value){ alert('Please enter a first name'); return false; }">
First name: <input type=text id=fn name=fname value=""><br>
If you do enter a first name and ListMail is still saying it is required (when it is enabled) then perhaps you have not set up your hidden form element on page 2 correctly. Does a "View source" show the data from page 1 in the hidden element?
Regards