data movingq;
  MonNum=month(today());
  MidMon=month(intnx('month',today(),-1));
  LastMon=month(intnx('month',today(),-2));
  do i=MonNum, MidMon, LastMon; 
     NextFile="Month"!!put(i,2.)!!".dat";
     NextFile=compress(NextFile,' ');
	    do until (LastObs);
	      infile xxx filevar=NextFile end=LastObs;
	      input Flight $ Origin $ Dest $ Date : date9. RevCargo : comma15.2;
		  output;
	    end; 
  end;  
  stop;
run;