ChartArea Max X value

Hi

Is there anyway of accessing a chart's Maximum X value.  i.e. the datetime of the far right of the visible area (similar to the TopY property for the Y axis) ?  I couldnt find anything except for LastVisibleBarIndex but this doesn't take into account any white space beyond the last bar (and the y axis scale). 

What i'm trying to do is to add some labels to certain lines that i've added to my chart but I want them to always appear on the far right of the chart and I need a suitable datetime for the DrawText time parameter.

Thank you