I'm wondering about several issues I have with drill down behavior on graphs: How can we visibly show that a certain graph is "drillable" (affordance issue). In more details:

1. On a single chart, how to show that a certain graph type (column against line) is "drillable"? (a mouse click will allow to see the same data in a different dimension)
2. On a single chart, how to show that a certain point on a graph is "drillable"?
3. On a single chart, Drill down only for this month forward - there is a vertical line that indicates the current month and data shows both the past and the future. Drill down is possible only from this month.