VIX 3.0.600 ,VIX power manager gone?

Go to the plugins menu, and under extensions, download a plugin called 'buyukbangpanel' - and this will give you a Scheduler, and that will allow you to do what you are wanting.

you can actually access the ViX timers as well by Menu - Timers - Power Timers. Press the green button to add the event. I think this is what you were looking for, or you can use the plugin I mentioned instead. (I should have mentioned this earlier - only I was being blind!)

no need for external plugins, the power manager feature was totally re-written and can now be found within the power timers section. This allows you to to what you want and much much more.