Drilldown report on a stacked bar graph

[rdp9090]

My chart at the moment looks like this:

 

So far, I've managed to do a proper drilldown that takes the text fields representing each section of the bars and clicking on those hyperlinks would display the proper tasks. However, I tried doing the same thing on the chart and no matter where I click on the chart, it only displays the 4 tasks in the last project (streamlining). What am I doing wrong with this? How do I make each section of the chart a separate link?