Full code after the jump.

View MXML

<?xml version="1.0"?>
<!-- http://blog.flexexamples.com/2007/09/25/using-the-tabnavigator-controls-taboffset-style-in-flex-3/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">

    <mx:ApplicationControlBar dock="true">
        <mx:Form>
            <mx:FormItem label="tabOffset:">
                <mx:HSlider id="slider"
                        minimum="-100"
                        maximum="100"
                        value="0"
                        snapInterval="1"
                        tickInterval="10"
                        dataTipPrecision="0"
                        liveDragging="true" />
            </mx:FormItem>
            <mx:FormItem label="horizontalAlign:">
                <mx:ComboBox id="comboBox">
                    <mx:dataProvider>
                        <mx:Array>
                            <mx:String>left</mx:String>
                            <mx:String>center</mx:String>
                            <mx:String>right</mx:String>
                        </mx:Array>
                    </mx:dataProvider>
                </mx:ComboBox>
            </mx:FormItem>
        </mx:Form>
    </mx:ApplicationControlBar>

    <mx:TabNavigator id="tabNavigator"
            width="100%"
            height="100%"
            tabOffset="{slider.value}"
            horizontalAlign="{comboBox.selectedItem}">
        <mx:VBox label="Panel 1" backgroundColor="haloOrange">
            <mx:Label text="TabNavigator container panel 1"/>
        </mx:VBox>
        <mx:VBox label="Panel 2" backgroundColor="haloGreen">
            <mx:Label text="TabNavigator container panel 2"/>
        </mx:VBox>
        <mx:VBox label="Panel 3" backgroundColor="haloBlue">
            <mx:Label text="TabNavigator container panel 3"/>
        </mx:VBox>
        <mx:VBox label="Panel 4" backgroundColor="haloSilver">
            <mx:Label text="TabNavigator container panel 4"/>
        </mx:VBox>
    </mx:TabNavigator>

</mx:Application>

View source is enabled in the following example.