CAK CTLR OBSERVES PREVIOUSLY CLRED LEARJET TURN TOWARDS WRONG ARPT AND TAKES ACTION TO RESOLVE SIT.

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ILS RWY 19/23 IN USE. THE CRJ AND LRJ WERE INBOUND FROM SW TO CAK WITH BOTH AT 5000 FT AND APPROX 7-8 MI IN TRAIL. WHEN THE LRJ WAS 9 MI NW OF CAK; HE ASKED FOR RWY 19 ILS; SO I HURRIEDLY TOLD HIM TO JOIN; SINCE HE WAS CLOSE TO THE LOC. I THEN TOOK THE CRJ TO 4000 FT; THEN THE LRJ TO 3000 FT; STILL ABOUT 6-7 MI AWAY FROM EACH OTHER ON PERPENDICULAR COURSES. THE LRJ WENT THROUGH FINAL SO I CONTINUED THE TURN TO 260 DEGS. I ASKED IF THE LRJ HAD THE FIELD FOR VISUAL; SINCE HE; 15 MI EARLIER; RPTED BASES AT 8000 FT. HE GOT THE FIELD; SO I CLRED HIM FOR VISUAL TO RWY 19. THEN I TOOK THE CRJ TO 3000 FT FOR VISUAL APCH; STILL ON A 050 DEG HDG. I NOTICED THE LRJ TURNING N TO AKR *7 MI N OF CAK). I CALLED TWR TO TELL HIM TO BREAK THE LRJ OUT. I LOOKED AT CRJ AND QUESTIONED HIS ALT AND TO MAINTAIN 4000 FT. I THOUGHT AT THAT POINT THAT I STILL HAD THE CRJ AT 4000 FT; BUT HE WAS DSNDING. I REITERATED TO THE CRJ TO MAINTAIN 4000 FT FOR THE TFC GOING TO THE WRONG ARPT. TWR PUTS THE LRJ ON A 270 DEG HDG AND 3000 FT. I HAD THE CRJ ON CLBING TO 4000 FT ON A 090 DEG HDG (LOWEST OBSERVED ON THE CRJ WAS 3000 FT; AND THE LOWEST ON LRJ WAS 2700-2800 FT AND APPROX 3 MI; EVEN THOUGH ON TAPE I SAID TO ANOTHER ACFT '2 MI' TO ITERATE THE SERIOUSNESS OF THE SIT). BOTH THEN LANDED WITHOUT FURTHER INCIDENT.