Can I forward specific callers to voicemail?

I want to set up call forwarding for a couple of specific numbers to kick them to voicemail.  Am I able to do this?  I assume if I block a number, they cannot get through to me at all, which is not what I want at this time, I just want the callers to go to voicemail so I can deal with them later.  I have searched and searched and cannot find a way to do this.