SO jQuery Fiddle

Test Fiddle mainly for SO Questions jQuery 1.4.3, UI 1.8.5

by Nick Craver

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.5/themes/ui-lightness/jquery-ui.css">
<select id="selEditRegion_" multiple size="10">
    <option value="1">Something</option>
    <option value="2">Something</option>
    <option value="3">Something</option>    
    <option value="4">Caribbean</option>
    <option value="5">North America</option>
    <option value="6">Something</option>
    <option value="7">Something</option>
    <option value="8">Middle East</option>
</select>

JavaScript

var res = "4^Caribbean,8^Middle East,5^North America", trade_alert_id = "";

$.each(res.split(','), function() {
  var thisval = this.split("^")[0]
  var thistext = this.split("^")[1].toString();
  $('#selEditRegion_' + trade_alert_id + ' [value*=\'' + thisval + '\']').attr('selected','selected');
});