ZOB CTLR EXPERIENCED OPERROR AT FL200 WITH CRUISE AND DSCNT ACFT.

Narrative

I WAS WORKING LFD SECTOR WITH INBOUND TO DTW; 1-2 OVERFLTS AND A FLT OF 4 F16'S NWBOUND WITHOUT A D-SIDE YET ASSIGNED. I HAD TO VECTOR THE F16'S W FOR THE CLB; VECTOR A DTW ARR E AROUND THEM AND HAD ANOTHER DTW INBOUND FROM S. I ALSO HAD A DTW ARR OVERTOP OF THE F16'S. I HAD A DEP TO MDW CLBING TO 16000 FT WHEN I GOT A RPT FROM ZAU THAT AN ACFT; JUST LEAVING MY AIRSPACE TALKING TO THEM; HAD RECEIVED MODERATE ICING AT 16000 FT IN MY AIRSPACE. I INFORMED THE ACR AND HE ASKED FOR A CLB. AFTER THAT; I HAD TO RECOORDINATE THE POINTOUT AND CLB WITH 2 DIFFERENT SECTORS IN ZAU SINCE A HDOF WAS ALREADY INITIATED. I ALSO HAD TO COORDINATE WITH DTW APCH A DSCNT FOR THE DTW ARR BECAUSE HE HAD TO STAY AT ALT DUE TO THE F16'S. THE F16 FLT; ALL 4 ACFT; HAD THEIR XPONDERS ON WHICH CAUSED THE TRACK TO GO INTO A COAST MODE AND I WAS UNABLE TO VERIFY THE POS OF THE LEAD AND TAIL ACFT. I INSTRUCTED THE LEAD TO SQUAWK ACCORDINGLY. I COORDINATED WITH THE SECTOR TO THE S TO HAVE THE DTW INBOUND STOPPED AT FL180 FOR TFC (F16'S). I TURNED THE DTW INBOUND FROM THE SW TO A 70 DEG HDG FOR THE F16; THEN DSNDED HIM TO FL190. THEN I NOTICED THAT THE 2 DTW INBOUNDS WERE TFC SINCE THE S ARR WAS NOT YET AT FL180. I INSTRUCTED HIM TO EXPEDITE THE DSCNT; STOPPED THE OTHER ARR AT FL200; THEN ISSUED TURNS TO BOTH ACFT. THE CONFLICT ALERT ACTIVATED AND MY ACTIONS WERE NOT SUFFICIENT FOR SEPARATION. A D-SIDE WOULD HAVE BEEN ABLE TO REDUCE MY WORKLOAD WITH THE EXTRA COORD AND ENABLE ME TO SCAN THE ENTIRE SECTOR BETTER. I WOULD HAVE BEEN ABLE TO RECOGNIZE THE SIT EARLIER AND PREVENT IT.