Follow me to google voice

I have a question about follow me.

Right now, I have follow me setup to send calls to cell phones after so many second of ringing an extension. Depending on that the cell phone user does, ignore call or miss call, a voice mail might be left on freepbx or the cell phone voicemail (google voice).

What I’d like to do is have follow me send the caller to google voice voice mail after ringing the cell phone in both an ignore call and unanswered call situation.

Anyone know how to do this?