%macro m1(stock = );
data wk1;
if &stock < 999 then s = trim("000"||"&stock");
else if &stock < 9999 then s = trim("00"||"&stock");
else if &stock < 99999 then s = trim("0"||"&stock");
else s = trim(" "||"&stock");
run;
data wk2;
set wk1;
call symput('z',s,'G');
run;
%mend m1;
%m1(stock = 875) %put &z;