If you have gauge objects then you can attach actions to those to set variables to either change the expression on a chart or show/hide a chart. Otherwise you can use a text object for the user to click on.
I understand your problem. There is no click event in containers to know when you are switching between QTD and YTD chart. I think the best solution is to replace your container with buttons that toggle variables. Then as in the examples posted by Steve, conditionally show one chart or another based on the variables.
You can do the same thing in the gauges or you can test the variable in the expression to conditionally calc QTD or YTD.