Why not try IF logic in the JCL. Force your rexx step to return something other than a 0 return code.
// IF (ABEND | RC = 0 ) THEN
//SUPERC EXEC PGM=SUPERC,TIME=1
//SYSPRINT DD SYSOUT=*
//OLD DD DSN=dsn1,DISP=SHR
//NEW DD DSN=dsn2,DISP=SHR
// ELSE
// ENDIF