vtiger

[hradac]

I hope someone can help me out with this. It seems so simple but I have been having a great deal of trouble tracking down a solution.
We use vTiger 5.0.3 for our invoicing. We already have the auto incrementation of the invoice number set up and the invoice number field is automatically filled in with it. What I would like to do is copy the invoice number to the subject field automatically as well.
Alternatively if I could make the subject field a non-mandatory field that would be good too. I don't know whether or not the subject field information is used as a key value in the database or not.
Admittedly I don't know very much about vTiger I came into this just a few days ago. The system was already set up so I lack a certain basic knowledge. I've done a bit of searching about this topic and the one post I found about it the response was something like "oh yeah that sound be easy." I'm sure it is but I just don't see it.
Thanks for any help.

[hradac]

For all those who looked at my original post I've found a solution.
At the end of the modules/Invoice/EditView.php file copy in the following code before the closing "?>" :

echo("<script language=\"javascript\" type=\"text/javascript\">
var xt = document.getElementsByName(\"subject\")[0];
xt.value=\"".$invoiceno."\";
</script>");

By the way this would have been much easier if the 'subject' text field had been assigned an 'id' attribute. My problem wasn't really with vTiger but with accessing the DOM properly.