Event reporting

Hi

I can find a list of multiple events attached to a single individual no problem, however when I reverse this and try and list the individual (and others like them) as attending multiple events I can't get it to work.

What I want is a report which, in simple terms, says.....

Give me all the contacts who have attended both event A and event B. The list should not contain people who have attended only one of them.

Thanks

Graham