Greetings Excel gurus,

I'm looking to create a Venn diagram that depicts not only relationships
among entities but also their relative size. For example, Group A is of size
60, Group B, size 30, is a subset of A; Group C, size 20, is also a subset of
A, and includes an overlap of 15 with group B. In other words, B & C are
partially overlapping, and both fully included in A. I would like the
circles' areas and the overlapping portion to be proportionate to their
sizes.

Does anybody know how this can be done? (It doesn't have to be in Excel if
someone can recommend a better tool or application for this process, ideally
in Office 2007 or a freely downloadable piece of software.)

Thanks for any suggestions or pointers.

--Nevet