Then check out EyeSee:
(Smalltalk at: #ConfigurationOfEyeSee) loadDefault
It is easy to create diagrams with it. Check out the examples in class "ESExamples".
I tried it in Pharo 1.2 - some examples were broken since the class Circle was removed. This is currently discussed on pharo-list. However - it's easy to fix.
Next time I need some visualizations I use Pharo instead of Excel ;)