Pie Chart question

[vonkoba]

Hi guys,
I'd like to create a Pie Chart where the values can be superimposed. That means that one of the charts can take lets say 80% of the chart and another value 50%, meaning I would have an area of 30% where both graphs superimpose. It'd also be great if the area of superimposition could be of another color or texture. I am attaching a bad picture of what I mean, just for you guys to have an idea. In here the space painted yellow would be the area where the red and the blue circle superimpose.
Can that be done in excel? If not, is there any other program that can do so? I played around a little bit with it, but couldn't figure it out . Thanks a lot for the help!
Charly

[tuph]

You may find something here:

http://peltiertech.com/Excel/Charts/ChartIndex.html

[vonkoba]

Thanks for your reply tuph , but I couldn't find it there.
I guess the problem is that the pie chart always thinks in terms of numbers, not percentages. If (just as an example) I am interested to visualize the percentage of cells that respond to drug 1 (let's say 80%) and drug 2 (60%), I would want a pie chart that shows a circle with 80% of its area with one color and the remaining 60% with another. Then I'd have an area in the middle with BOTH colors that would represent the percentage of cells that are susceptible to BOTH drugs at the same time (the rest of the cells respond to one drug OR the other). In excel the pie chart never "thinks" in terms of percentages but in terms of numbers, so if my values are 80% and 60% then excel does the following calculation: 80+60= 140. Then it does a graph where 80 = 57% of 140 and 60 = 43% of 140 . Thus the slices never ever superimpose!
Thanks anyway!