Hi,  My problem is about calculating the cumulative sum for each id and for each date taking into account a sliding period of 15 previous days. If the cumulative sum exceeds 10k, the variable top is incremented. The treatment is done for June only.   Here is an example of the desired result :  id app_date price cum top  1 29-juin-20 4000              4 000 . 1 13-juin-20 5000            45 000 1 1 13-juin-20 6000            40 000 2 1 11-juin-20 7000            34 000 3 1 10-juin-20 8000            27 000 4 1 01-juin-20 9000            19 000 5 1 30-mai-20 10000            10 000 . proc sort data = tab out= tab1; by id descending app_date; run;   data tab2; set tab1; %let annee=2020; %let month=06; by  id; retain last_date date_last_d CUM; if first.id then do;       last_date =app_date;       date_last_dem = app_date;       CUM=0; end; if month(date_last_d) =&month. then do ; diff= date_last_d -app_date; CUM= price+ CUM; end; if diff>15 then do;       diff = .;       CUM =.;       last_date =app_date;       date_last_d = app_date; end; if last.id and CUM>10000 then top= top+1 ; output; last_date=app_date; format last_date DDMMYY10.; format date_last_d DDMMYY10.; format CUM 14.2;   run;   I can do it for the first iteration but I cannot do it for all the lines.   Thank you, ... View more