How to prevent tray notifications from queuing when not viewable

I have a .NET application that runs minimized in the system tray and provides notifications when certain actions take place. When the user is not logged in or has the screen locked, these notifications are evidently queuing so that the next time the user logs in they are sequentially presented with all the expired notifications. What I would like to do is prevent notifications from being presented if the user can't see them (logged out or locked screen). Or, if it is easier, configure it so that the user doesn't see all the notifications they missed while logged out. Looking for best practices for such a case. Thanks.