Using Hazel on "server"

In a network of 4 Macs, one is used as a depository for the files all users need to access. It is not a server in the technical sense. Users on all other Macs have a login item for the folder which contains those files, so the "server" is always mounted after login.
These files are order forms; their label indicates their status, like "Blue" = "to be confirmed by client".
I intend to install Hazel on the "server" to run a script on those forms, according to their label.

How can I get a message to a user on another Mac?
I'd like to notify users when something goes wrong.

Or would it be possible (and simpler, message-wise) to run Hazel in those user accounts, not on the "server"?
Would that not cause 'collisions' of some kind, with 3 instances of Hazel watching the same folder?

NotaBene: Macs run both Tiger and Leopard, don't know if that's relevant.

It's a bad idea to have multiple Hazel's on multiple machines monitoring the same folder, as you've surmised.

One way you can do this is by using Growl (http://www.growl.info). Growl can be set to forward notifications to other machines. So, you can have Hazel send Growl notifications and have Growl (on the server) forward them to each of the clients. From the looks of it, it's an all or none deal as far as sending over the network is concerned (i.e. you can't control which notifications get sent over the network). If the server isn't really used for anything else, then it might not be a big deal otherwise, maybe you can filtering on either the client or server so you don't get hit with random Growl messages on the server. In any case, check out the "Network" tab in Growl.

If you try this out, report back as I'm curious as to whether it works out.

Yes, of course. Forgot about Growl.

There won't be a problem with multiple notifications; they don't use Growl.
I'm still trying to figure out their workflow, so reporting back will be some time.

Thanks, Paul

It's a bad idea to have multiple Hazel's on multiple machines monitoring the same folder

Is it the monitoring itself which is problematic, or the multiple triggering of a rule on some file? Maybe this the same thing...

It's a waste of resources and if a rule is triggered, they could end up interfering with eachother. Plus, it's always best to run Hazel on the machine that hosts the drive as it then has access to more metadata.

Well, I've decided not to try network notifications with Growl.
There's too many reports of it not working, and the Growl crew don't seem to see a way for solving those problems.

I'm now looking into mailing notifications.