I did this a few months ago. Earliest appointment I could get was 4 months out. I ended up doing a walk-in appointment at the ATL airport. I had to leave without doing interview twice due to running out of time while in waiting area. They won't turn you down for a walk-in appointment, but it could take 2-3 hours.

Fwiw, I think it's sucks how our company recommends global entry, but won't pay for it. American and United pay for it for their crew members.