I can't get the samples to work, much less take a stab at the problem. Apparently under WinNT4 "Your vendor has not implemented the macro AddNotifyIcon." But I had a thought:

Consider MS KB Article Q162613. In it, there's a description of the API as seen through visual basic. The difference between an "Add", "Change" and "Remove" in the API appears to be 1 argument. The VB call is to "Shell_NotifyIcon" which looks an awful lot like the "NotifyIcon" method call that Win32::GUI uses. Can someone (who can get this to work) hack at the API a little bit to see if these are indeed the same call. And if possible change the argument of "0" (ADD) to "1" (MODIFY). It might get you some of the way there...