Gift certificate decimal separator and required message field

I have 2 questions about the form in gv_send_default.php.

1. When a costumer want to send a gift certificate he must fill in the form. All the fields are required to fill in exept the message field.

How can I change it so that the message field is a required field too en the costumer who wants to send the gv is forced to fill in his own text?

2. When filling in the value of gift certificate the costumer has to fill a "." as the decimal seperator. When the costumer uses a "," al the numbers after the "," disappear ie 17,95 becomes 1795,00. How can I change it so the costumer can use the "," which is the standard decimal separator for the Euro.

Thanks in advance for your help!

I've question 1 solved! In header_php.php the first "if" was set on "false" . I changed it in:

if ($_GET['action'] == 'send') {
$_SESSION['complete'] = '';
$error = true;

So for that part is works fine.

I only need an answer on question 2. I hope somebody can help me or give me a hint in the right direction.

I thought I had solved question 1, but no. I hope somebody can help me!