How can I create a popup that appears when a user logs in?

[Shrike]

I need the computer to show a popup window with a message of my choice whenever any user logs on. Nothing fancy, simple text would be fine. I'm running OS X on a G5. Also, I'm not really experienced on Macs (sorry!), so if you could keep the explanations as simple as possible, I would really appreciate it.
Thanks in advance!

 

[g5orbust]

This would require use of Applescript, which is something I have no idea how to use

I suggest asking this same question on www.macrumors.com (NOTE: I only redirect here when I dont know how to answer) and asking the people there. There is bound to be someone there who knows how to use Applescript.

 

[Shrike]

Thanks for the tip! I'll go give them a shout.