Model any windows in the shaded wall the Monthly Shading Schedule.
If completely shaded use the shaded air Option for what lies beyond the wall.
If partly shaded you can reduce the absorptance of the wall. e.g. if the absorptance is 0.8 and the wall is ¾ shaded then the absorptance would be reduced to ¼ of 0.8 i.e. 0.2.