changing jqm css style from a function

changing jqm css style from a function

Hi JQM Gods-

I'm stuck and I hope you can help. I'm new to development and I'm not quite sure where my thinking is wrong here.

In my header toolbar I have two buttons for select lists. I've figured out how to put a pointer on top of the select list popup that points to the button tapped. I can't figure out how to change the position of the pointer when the user taps a different button. 

I added a line in the .ui-popup-container:after style that aligns the arrow under button 1 (left:90px). To align it under button 2 it needs to be left:120px. It seems the thing to do is write a function to change the line in .ui-popup-container:after to left:120px. I've looked through the forums for similar problems (popup positioning, overriding CSS styles with functions) and tried a bunch of different things. Nothing works. 

Can someone here help me think about it in the right way?

Thanks in advance and here's the code:

<!DOCTYPE html> 

<head>

<title>Popup Fail</title>

<meta name="viewport" content="width=device-width, initial-scale=1"> 

<link rel="stylesheet"  href="http://code.jquery.com/mobile/latest/jquery.mobile.css" /> 

<script src="http://code.jquery.com/jquery-1.8.0.min.js"></script> 

<script src="http://code.jquery.com/mobile/latest/jquery.mobile.min.js"></script>

<style type="text/css">

.ui-popup-container {

width:90%;

padding:0

}

.ui-popup-active {

top:45px !important;

}

.ui-popup-container:after {

content: ' ';

height:0;

position:absolute;

width:0;

border:10px solid transparent;

border-bottom-color:#ffffff;

bottom:100%;

left:90px;

  opacity:0.9;

}

</style>

<script language="JavaScript">

    $(document).ready(function(){

      $(".navButton2").bind("tap", function(event) {

        $('.ui-popup-container:after').css('left':'120px');

      });

    });

</script>

</head>

<body>

<div data-role="page">

<div data-role='header' data-position='fixed' >

<div class='ui-grid-c' style='height:44px;text-align:center;vertical-align:middle'>

<div class='ui-block-a'>

</div><!-- /block a -->

<div class='ui-block-b' id='navButton1'>

<select name='Day' id='Day' data-mini='true' data-native-menu='false' data-icon='false'>

<option value='Today'>Today</option>

<option value='Tomorrow'>Tomorrow</option>

<option value='DayAfter'>The Day After</option>

</select>

</div><!-- /block b -->

<div class='ui-block-c' id='navButton2'>

<select name='Time' id='Time' data-mini='true' data-native-menu='false' data-icon='false'>

<option value='AM1'>Morning</option>

<option value='AM2'>Afternoon</option>

<option value='PM1'>Evening</option>

<option value='PM2'>Night</option>

</select>

</div><!-- /block c -->

<div class='ui-block-d'>

</div><!-- /block d -->

</div><!-- /ui grid c -->

</div><!-- /header -->

<div data-role='content'>

<h3>This page intentionally left blank</h3>

</div><!-- /content -->

<div data-role="footer" class='ui-bar'>

<p>Here's the footer</p>

</div><!-- /footer -->

</div><!-- page -->

</body>

</html>