Как-то так. Код пояснить нужно?
Код:<!DOCTYPE html>
<html>
<head>
<title></title>
</head>
<body>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"></script>
<script type="text/javascript">
var reload_time = 5000;
$(document).ready(function(e) {
$('#time').click(function() {
reload_time = $("#time").val();
});
});
function reload_chat(){
$('#currentElement').attr("src", $('#currentElement').attr("src"));
timeout_id = setTimeout("reload_chat()",reload_time);
} timeout_id = setTimeout("reload_chat()",10);
</script>
<select id="time">
<option value="5000">5</option>
<option value="10000">10</option>
<option value="20000">20</option>
</select>
<iframe src="sddsf.html" id="currentElement"></iframe>
</body>
</html>