Create the Bar-line Chart.The Y2AXIS option assigns the line plot to the Y2 axis.

proc sgplot data=sashelp.stocks (where=(date >= "01jan2000"d
                                 and date <= "01jan2001"d
                                 and stock = "IBM"));
   title "Stock Volume vs. Close";
   vbar date / response=volume;
   vline date / response=close y2axis;
run;