Its actually a reasonable request I think. If they want to
see all the graphed categories for a month they click the month
label. If they want to see the sub-categories of a category for a
month, THEN they'd click the data point for the line (or bar or
area etc) for the month. Seem totally intuitive to me. I like it.
However I dont know how to do it.
The Category axis does not seem to have any default events.
Is there a way to add an event handler to an object that does not
have it by default?