Use double set with key lookup to account for missing dates, similar to my previous method using double set statements and point:
data foo(index=(date /nomiss /unique));
call streaminit(12345);
do date='01JAN1960'd to today();
count=int(rand('uniform')*10e2);
if rand('table',.95)=1 then output;
end;
format date date9.;
run;
data bar;
set foo(rename=(date=_date)) nobs=nobs;
sum=.;
miss=0;
do date=_date-10 by 1 while ( date < _date and _n_ > 10 /* and miss=0 */ );
set foo key=date/unique;
if _iorc_ then do;
_iorc_=0;
_error_=0;
miss+1;
end;
else do;
sum+count;
end;
end;
*if miss>1 then call missing(sum);
date=_date;
drop _date;
run;
