You can try a variety of different 3rd party clock applications that support alarms and just set the alarms on them so that they don't interfere or clutter your calendar.
A few comes to mind like
BigClock and
Watchmaker. Both are free. I prefer Watchmaker since it looks very nice in high resolution and supports all the midi sounds you may have on your Treo. There are others that aren't freeware like
TreoAlarm,
Palmary Click and others.