Event handler if new File added in current folder

Hi folks,

I'm just trying to write a little jsx script for Bridge CS6.

How can I implement an event handler that will react if the user adds a new thumbnail (new file) to the current folder in bridge.

I've tested it with this code, but it doesn't work:

app.document.thumbnail.watch ("children", function(id, oldVal, newVal) {      $.writeln (oldVal + " to " + newVal);      // some code here });

Thanks. Greetings