Here is a sample, wehre you can see how it ist possible to populate form fields with a javascript generated content
<HTML>
<HEAD>
<TITLE>Test</TITLE>
</HEAD>
<BODY>
<p>Content of myField: <?=$myField?></p>
<form method="POST" action="<?=$HTTP_SERVER_VARS["SCRIPT_NAME"]?>">
<input type="hidden" name="myField" value="<?=$myField?>">
</form>
<script language="JavaScript">
if (document.forms[0].elements[0].value == "") {
var myField = new Date();
document.forms[0].elements[0].value=myField;
alert (document.forms[0].elements[0].value);
document.forms[0].submit();
}
</script>
<br><a href="<?=$HTTP_SERVER_VARS["SCRIPT_NAME"]?>?myField=">again ...</a>
</BODY>
</HTML>