Challenging iCal with repeating event...

Hello,

I want to add some repeating multi-day festivals to my iCal.
These events have some challenging rules for iCal.

For example:


This year it is from 21 to 27 of July.

I don't know how to tell iCal this rule. The only thing I could discover is the 'last weekday' or 'last weekendday' of a certain month, but that is actually something different...

Thanks,