[flexcoders] Horizontal Axis on top and bottom of a bar chart

[Nate Pearson]

I know this is easy but I can't figure out to do it!

I want to put a horizontal axis on the top and bottom of my bar chart.
 Exact same horizontal axis.

Is it a property I set?  I can't seem to find it.
Here's my horizontal axis:

<mx:horizontalAxis>                                             
        <mx:DateTimeAxis  id="chartDTAxis" dataUnits="months"/>  
</mx:horizontalAxis>

Thanks,

Nate