Adding exclusions in a recurrence rule

[MacTI]

I'm a bit lost. I'm working on integration between ZCS and a Web app, and one of the thing I have to do is creating events that might have exclusions (event recurring at X days, but not at day Y). soap-calendar.txt says that I can add the <exclude> element to <recur>, but how do I specify the excluded dates? In the sub-elements of <exclude>, only start dates are accepted.

And I can't found an example because neither ZCS web client or my iPod touch have the GUI to create exclusions...