function ss = dirstruct40_ (sdir)
  % sdir = "L:\\QualData\\CalibrationLog"
  % returns full FN of all txt log files
  ss={};
  dd1=dir(sdir);
  frac = 0;
  hwb =  waitbar(frac, "Wait until process folders...");
for jj=1:length(dd1)
    name1 = dd1(jj).name;
    if (length(name1) == length("0710814_ttt")) &&...
            (strcmp(name1(1:7), "0710814") || strcmp(name1(1:7), "0826819"))
        sdir2 = fullfile(sdir,name1);
        dd2=dir(sdir2);
        for ii=1:length(dd2)
            name2 = dd2(ii).name;
            if (length(name2) == length("f_20210408_111050.txt")) &&...
                (strcmp(name2(end-3:end), ".txt"))
                fn3 = fullfile(sdir2,name2);
                ss=[ss,fn3];
            end % if
        end % for
        frac = double(jj)/length(dd1);
        waitbar (frac, hwb);
    end % if
end % for
  close(hwb)
end % function