proc format;
 	invalue sexn
		'F'=1
		'M'=2
		'N'=3
		other=4;
	value sexo
		1='Female'
		2='Male'
		3='Not reported'
		4='Missing';
 run;

 data _adsl;
 	set adam.adsl;

	sexn=input(sex, sexn.);
	keep usubjid sex sexn;
 run;

 proc freq data=_adsl noprint;
 	table sexn*sex / out=fqsex;
 run;


 
 %macro fill_format(din=, var=, fillfmt=);
	 proc format cntlout=_fillfmt0;
	    select &fillfmt;
	 run;

	 data _fillfmt1;
	 	set _fillfmt0;

		&var=input(strip(start), best.);
	 run;

	 proc sort data=&din; by &var; run;
	 proc sort data=_fillfmt1; by &var; run;
	 data &din._o;
	 	merge _fillfmt1(in=a keep=&var label) &din(in=b);
		by &var;
		if a or b;
	 run;
 
%mend fill_format;


%fill_format(din=fqsex, var=sexn, fillfmt=sexo);