Indsætte javascript som value i form

<body>

<SCRIPT LANGUAGE="JavaScript">

<!-- Begin
var useragent = navigator.userAgent;
var bName = (useragent.indexOf('Opera') > -1) ? 'Opera' : navigator.appName;
var pos = useragent.indexOf('MSIE');
if (pos > -1) {
bVer = useragent.substring(pos + 5);
var pos = bVer.indexOf(';');
var bVer = bVer.substring(0,pos);
}
var pos = useragent.indexOf('Opera');
if (pos > -1)    {
bVer = useragent.substring(pos + 6);
var pos = bVer.indexOf(' ');
var bVer = bVer.substring(0, pos);
}
if (bName == "Netscape") {
var bVer = useragent.substring(8);
var pos = bVer.indexOf(' ');
var bVer = bVer.substring(0, pos);
}
if (bName == "Netscape" && parseInt(navigator.appVersion) >= 5) {
var pos = useragent.lastIndexOf('/');
var bVer = useragent.substring(pos + 1);
}

screenheight = screen.height
screenwidth  = screen.width


document.write(bName);


</script>


<form name="form1" method="post" action="update.php">

        <input type="hidden" name="browser" value="">

        <input type="submit" name="Submit" value="Submit">

</form>



</body>

Hvordan får jeg "document.write(bName);" indsat som value i formen?