You can only check your bag through to your final destination. They will not short-check it for you unless your layover exceeds a certain length which I believe is 12 hours but I could have that detail wrong. Also, in the event of IROPs, DL is only obliged to get you to your final destination, not necessarily to route you through ATL. If the meeting is that important that you don't want to risk missing it, I suggest you change your itinerary and pay the fare difference and change fee if any.