<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/07/18/setting-the-dropdown-menu-border-thickness-and-border-color-on-a-combobox-control-in-flex/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="top"
        backgroundColor="white"
        initialize="init();">

    <mx:Script>
        <![CDATA[
            import mx.controls.ComboBox;

            private var arr:Array;
            private var comboBox:ComboBox;

            private function init():void {
                arr = [];
                arr.push({label:"One"});
                arr.push({label:"Two"});
                arr.push({label:"Three"});
                arr.push({label:"Four"});
                arr.push({label:"Five"});
                arr.push({label:"Six"});
                arr.push({label:"Seven"});
                arr.push({label:"Eight"});
                arr.push({label:"Nine"});
                arr.push({label:"Ten"});

                var myDropdownStyleName:CSSStyleDeclaration;
                myDropdownStyleName = new CSSStyleDeclaration(".myDropdownStyleNom");
                myDropdownStyleName.setStyle("borderColor", "haloBlue");
                myDropdownStyleName.setStyle("borderThickness", 5);
                myDropdownStyleName.setStyle("fontWeight", "normal");

                comboBox = new ComboBox();
                comboBox.dataProvider = arr;
                comboBox.setStyle("dropdownStyleName", "myDropdownStyleNom");
                addChild(comboBox);
            }
        ]]>
    </mx:Script>

</mx:Application>