Flex 4 chart tooltip help.

[porticue]

I have a bit of a specialized need. I have an AreaChart where I need
to have the tooltip rollover activate when rolling over any area of
the chart. At that time the time span between the two points would
highlight and show a tooltip. I'm not quite sure what I should be
looking for in order to do this, or if I'm explaining what I want to
correctly. Below is a link to an image of the chart I currently have,
and the second is a mockup of what I'm trying to achieve. Hopefully
that helps. Thanks

Chart:
http://porticue.com/uploads/flex/chart.jpg

Mockup:
http://porticue.com/uploads/flex/rollover.jpg

Andrew