Using the LineChart component of Flex: How do I make the horizontal grid lines (background within the chart) dotted? With the mx:Stroke within the mx:horizontalStroke, I can only set properties like weight, color and alpha. I'd like to make the line dotted...

This is what I have now:

<mx:LineChart id="linechartDays" width="100%" height="100%" dataProvider="{dayData}" showDataTips="true">
    <mx:backgroundElements>
    	<mx:GridLines horizontalChangeCount="1" direction="horizontal">
    		<mx:horizontalStroke>
    			<mx:Stroke weight="1" color="0xcccccc"/>
    		</mx:horizontalStroke>
    	</mx:GridLines>
    </mx:backgroundElements>
</mx:LineChart>