I think that the count function does what you are looking for:

*Replicate data;

data dt;
infile cards dlm = ",";
length stat $30;
input stat;
cards;
Closed Open Open,
Closed Closed Open,
Open,
Open,
;
run;

*Compute countOpen using count;

data dt2;
set dt;
countOpen = count(stat, "Open");
run;

proc print data = dt2;
run;