After a bit of help.
iLogic is best for that type of scenario. I have seen an example of it on the forums and in the help/tutorials in 2011/2012. Have a look at this link http://wikihelp.autodesk.com/Inventor/enu/2012/Hel
Only trouble is it takes you to a dataset for 2013. There used to be a good tutorial on a flange for your exact scenario, but I can't track it down. I'm sure someone on the forums will point you to the exact files.
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