hi, read this from http://ez.no/developer/forum/developer/xajax_developers
I haven't tried specifically xajax, but typically while working with YUI for example, I would create a new module/view where one of the params is a node_id something like
www.example.com/handlerequest/23
Then sending async get call you can get what you want from that URL as on PHP level you can fetch node_id = 23 then generate either XHTML output or whatever you need. You can pass of course more params, like www.example.com/handlerequest/23/JSON, where last part can be use for decision what output return.
You duty first create a module which interact directly with your XMLHttpRequest
or you can use xajax http://ez.no/developer/contribs/applications/xajax
Other article on Ajax http://ez.no/developer/articles/clean_up_your_applications_using_ajax