Here's what I'm doing:

As part of a big project, I'm trying to tie in multiple status-monitoring applications into a single "dashboard" page that will display a good representation of a summary of each monitoring tool. Currently this page has 3 tools tied in, but this will grow into a much larger number rather quickly (3 more within a week of finishing tying in these 3, for example).

Here's how I'm doing it:

Basic screen scraping - I issue an HTTP request from the server to the tool, grab the piece I want, then display it. You can see that even with only 3 tools currently this takes some time, and this will only grow longer with more tools. The obvious solution to reducing or at least hiding this delay is to scrape asynchronously - this is where my beloved AJAX comes in.

Here's my problem:

To reduce the impact of a single slow tool bogging down the entire application, I'm trying to issue an AJAX request for each tool. The problem I'm having is that I can't figure out how to tell each object which tool it represents! After Googling for quite some time, I came across what I thought would work:
http.onreadystatechange = function(args){if(http.readyState==4){alert(args)}};
Sadly, that doesn't work - args is undefined.

So, my question is thus: is it possible to do this without writing separate onreadystatechange handlers for each request? My initial idea was to simply give each tool its own onreadystatechange handler, but that will real quickly grow out of control! Any one have any suggestions?