alvin012:
In addition to Matthew's comment, you can use the Floor Plan Cut Plane assigned to the View to determine which level of windows appear in the wall if it is a single wall (this could also be done with stacked walls on different Stories).
You should add a Signature to your Profile (click the Profile button near the top of this page) with your ArchiCAD version and operating system (see mine for an example) for more accurate help in this forum.
David