You might want to try looking at ATL-MKE. It's $59 one way for travel Mon-Thur and Saturday.
Something like ATL-TYS-CVG-MKE will get you 1500 miles.
If you need something more than that, you can also route ATL-CVG-DFW-MKE (but not the other way). There's a daily DFW-MKE 1-stop flight which stops in CVG (DL 474, leaving DFW at 14:50).
Allowable routing for ATL-MKE:
<font face="Verdana, Arial, Helvetica, sans-serif" size="2">ROUTING 962 FROM-TO ATL-DL-CVG-DL-TYS/BNA/LEX/SDF/ IND-DL-CVG-DL-DFW-DL-MSN-DL-MKE*</font>