Did you save the script with the idle handler as a .app file with the "Stay Open" checkbox selected in the Save dialog?
This is required for the code within the idle handler to be run "on idle", else it won't run at all. Save it that way and try again.
You're checking windowList for missing value. This sounds like a condition where no FCE windows are open. If you want the block where you're scripting Growl to execute, it should be within the if statement, not after.
Also, depending on what version of Growl you're using, it might respond to one of "Growl" (v1.3+) or "GrowlHelperApp" (v<1.3), but not the other. To future-proof your script, replace
tell application "GrowlHelperApp
with the following:
tell application id "com.Growl.GrowlHelperApp"
All versions of Growl respond to that.
The block of code you have that triggers Growl looks like you modified their example, and from your comments it sounds like that's working fine.
You basically need to have your macbook output to two displays, which it won't do easily/willingly.
There are a couple hacks...either doing the display output over USB or using a matrox display. See more info: here
One really hacky solution might be to output via air display to and iPad (hooked up to a projector)for the 2nd monitor. I'll buy you a beer if you make that work. :-)
Best Answer
Currently there is no way to accomplish this. The Growl mailing lists have discussed allowing Growl to always place the notification on the display that you have a window focused in.
For example, you have 3 displays, oriented in a horizontal line, and you're doing some file management on the far-left display and web browsing on the far right. If Finder has focus, the notification will be shown on the far-left display, if Safari/Chrome/Firefox/$BROWSER has focus, the notification will be shown on the far-right display.
But this feature has not yet been implemented, so you are limited to explicitly configuring Growl to send notifications to a single display.
This feature has been written up on their Google Code Project page, so you can star the issue in order to receive further notifications.
Note that you can star it on an issue detail page by clicking the star outline to the left of the title "Issue 122: [...]", or at the bottom of the page just above the comment box. After clicking the star in either location, it will turn yellow and have a thicker blue outline, that means you've subscribed, and in essence, "voted" for the feature.