Trying to put my head around an idea

So i have a helpdesk staffer here that cannot remember sometimes to call forward all when they leave for lunch or in the evenings. I was trying to create a time condition for lunch and afterhours for their extension but i cannot figure out how and still retain VM capability. Is there a way to do this outside of misc app w/o voicemail to an extension? I can do time conditions externally but not to internal only extensions.