jquery slider游标step有关问题

jquery slider游标step问题.
step默认为10,现在是我要根据不同的取值变化,当$("#amount").val()大于等于90的时候,step为2,不知道如何解决.

JScript code

<script>           <script>        $(function () {            $("#slider-range-min").slider({                range:"min",                value:0,                min:0,                max:100,                step:10,                slide:function (event, ui) {                    $("#amount").val("$" + ui.value);                }            });            $("#amount").val("$" + $("#slider-range-min").slider("value"));        });    </script>    </script>

HTML code

<link rel="stylesheet" href="/css/base.css" type="text/css" media="all" />            <link rel="stylesheet" href="http://code.jquery.com/ui/1.8.19/themes/base/jquery-ui.css" type="text/css" media="all" />            <link rel="stylesheet" href="http://static.jquery.com/ui/css/demo-docs-theme/ui.theme.css" type="text/css" media="all" /><script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js" type="text/javascript"></script><script src="http://code.jquery.com/ui/1.8.19/jquery-ui.min.js" type="text/javascript"></script><STYLE>    div.demo { padding: 110px !important; }    </STYLE><SCRIPT>    $(function() {        $( "#slider" ).slider({                range:"min",                min:0,                max:100,                step:10,                slide:function (event, ui) {                    if(ui.value > 89){                        $(this).slider({step:1})                    }else {                        $(this).slider({step:10})                    }                    $("#test").html("$" + ui.value);                }        });    });    </SCRIPT><DIV class=demo><DIV id=slider></DIV></DIV><div id="test"></div>