Change the value of an Hidden field !!!!

Hello,

I want to change the value of an hidden field
I'm doing a OnChange on a select field : OnChange="new_value()"
And the function is :

<script language="JavaScript1.2">

function new_value();
document.name_form.name_hidden.value = document.name_form.name_select.value;
 }

</script>

It work with MSIE but not with Netscape.
Do you know what's wrong ?

Thanks

Sorry for my english