<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/05/20/changing-the-up-arrow-skin-and-down-arrow-skin-on-a-numericstepper-control-in-flex/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">

    <mx:Style>
        NumericStepper {
            downArrowSkin: Embed("assets/bullet_arrow_down.png");
            upArrowSkin: Embed("assets/bullet_arrow_up.png");
        }
    </mx:Style>

    <mx:ApplicationControlBar dock="true">
        <mx:Button label="Click here to remove focus from NumericStepper control" />
    </mx:ApplicationControlBar>

    <mx:NumericStepper id="numericStepper" />

</mx:Application>