PROCEDURE GEN_EXCEL IS

IN_FILE TEXT_IO.FILE_TYPE;
VC_HEAD Varchar2(32000);


BEGIN

IN_FILE := TEXT_IO.FOPEN('C:\'||'123.CSV','W'); 
TEXT_IO.PUT_LINE(IN_FILE,'EMPLOYEE DETAILS'||chr(10));
VC_HEAD := 'EMPNO,ENAME,JOB,MGR,SAL,COMM,DEPTNO';

TEXT_IO.PUT_LINE(IN_FILE,VC_HEAD);
FOR C1 IN ( SELECT EMPNO,ENAME,JOB,MGR,SAL,COMM,DEPTNO FROM EMP) LOOP

TEXT_IO.PUT_LINE(IN_FILE,C1.EMPNO||','||C1.ENAME||','||C1.JOB||','||C1.MGR||','||C1.SAL||','||C1.COMM||','||C1.DEPTNO);


END LOOP;

TEXT_IO.FCLOSE(IN_FILE);
MESSAGE('Excel file has been created!');
MESSAGE('Excel file has been created!');

EXCEPTION
WHEN NO_DATA_FOUND THEN
TEXT_IO.FCLOSE(IN_FILE);
MESSAGE('Error while writing file');
MESSAGE('Error while writing file');
END;

TEXT_IO.PUT_LINE(IN_FILE,'EMPLOYEE DETAILS'||chr(10));

Add a couple of commas before the string "employee details?"