[App_rpt-users] Using scheduler to play custom (local) voice announcement

Hi Guys: I'd like to play a custom ulaw announcement over my repeater (at say an hourly interval). This custom announcement is different from my repeater ID. I see that I can call a macro from the scheduler; I'm not sure whether I can invoke Asterisk's System command directly from a macro, or whether I have to make a call to a local extension that invokes the System command (which then plays my announcement). Hopefully there's an easier way! Appreciate some guidance. Thanks! Ramesh, VA3UV