Может так ?
<html>
<body>
<script language="JavaScript">
function gettxt(a)
{
var reg=/>(.*)<\//;
var arr=reg.exec(a)
setTimeout("gettxt()",100);
document.add.ankor.value=arr[1];
}
</script>
<form name="add" method="post">
<input type="text" size=20 name=post onchange="gettxt(this.value)" autocomplete="off">
<br>
<input type="text" size=20 name=ankor autocomplete="off">
</form>
</body>
</html>