%macro aocflag (inds=, outds=, flagvar=, sort=, cond=);

    data &inds.sub1 &inds.sub2;
        set &inds;
        if &cond then output &inds.sub1;
        else output &inds.sub2;
    run;

    proc sort data=&inds.sub1; by &sort; run;
    data &inds.sub1;
        set &inds.sub1;
        by &sort;
        if first.usubjid then &flagvar= 'Y';
    run;

    data &outds;
        set &inds.sub1 &inds.sub2;
    run;

%mend aocflag;

*** First USUBJID     *****;
%aocflag (inds=cm6, outds=cm7, flagvar=aocc01fl, sort=STUDYID USUBJID ATCTEXT1 ATCTEXT3 CMDECOD CMSEQ,
       cond=%str(prefl='Y') );
*** First ATCTEXT1 within usubjid    *****;
%aocflag (inds=cm7, outds=cm8, flagvar=aocc02fl, sort=STUDYID ATCTEXT1 USUBJID ATCTEXT3 CMDECOD CMSEQ,
       cond=%str(prefl='Y') );
*** First ATCTEXT3 within usubjid atctext1   *****;
%aocflag (inds=cm8, outds=cm9, flagvar=aocc03fl, sort=STUDYID ATCTEXT1 ATCTEXT3 USUBJID CMDECOD CMSEQ,
       cond=%str(prefl='Y') );
*** First CMDECOD within usubjid atctext1 atctext3    *****;
%aocflag (inds=cm9, outds=cm10, flagvar=aocc04fl, sort=STUDYID ATCTEXT1 ATCTEXT3 CMDECOD USUBJID CMSEQ,
       cond=%str(prefl='Y') );