sas Proc expand procedure - sas

Question

I am trying to calculate 3 months moving average of the following data by Product by country( I only have two country variables here). Is there a way to do so?
Here is the sales table I have:
Date Product Country Sales
201101 Sofa US 100
201102 Sofa US 200
201103 Sofa US 250
201104 Sofa US 300
201101 Sofa CA 250
201102 Sofa CA 300
201103 Sofa CA 250
201104 Sofa CA 300
201101 Chair US 300
201102 Chair US 300
201103 Chair US 300
201104 Chair US 300
201101 Chair CA 300
201102 Chair CA 300
201103 Chair CA 300
201104 Chair CA 300
I tried something like the following, but moving average is only calculated by country. Is there a way I can have it calculated by country, by product? Any ideas will be appreciated. thanks:)
PROC SORT DATA=Sales;
BY Country Product Date;
RUN;
PROC EXPAND DATA=Sales out =ma;
By Country Product;
CONVERT Value=Value_ma/transformin=(setmiss 0) transformout=(movave 3);
run;

Answer 1

after my comment i tested a bit, i guess concating product and country gives the result you are looking for (i hope i still did not understood something wrong):
data have;
input Date $ Product $ Country $ Sales ;
datalines;
201101 Sofa US 100
201102 Sofa US 200
201103 Sofa US 250
201104 Sofa US 300
201101 Sofa CA 250
201102 Sofa CA 300
201103 Sofa CA 250
201104 Sofa CA 300
201101 Chair US 300
201102 Chair US 300
201103 Chair US 300
201104 Chair US 300
201101 Chair CA 300
201102 Chair CA 300
201103 Chair CA 300
201104 Chair CA 300
;
run;
data have ;
set have;
copr=catx("_",Product,country);
run;
PROC SORT DATA=have;
BY copr Date;
RUN;
PROC EXPAND DATA=have out =ma ;
By copr;
CONVERT sales=average / transformin=(setmiss 0) transformout=(movave 3);
run;
proc print data=ma;
var date product country average;
where time > 1;
run;
result: