Once you had created some c2pWindow objects using Mc2pWindow, you may have made one of the objects the current main object to `use'. This may have been achieved with MUsec2pWindows, MUsec2pWindow or you may have created a c2pWindow object with `automatic use' switched on with MAutoUsec2pWindows On. In order to find the the number of the currently used c2pWindow object, you can use MUsedc2pWindow which will return the number of the currently used object.
Possible syntax:
MUsedc2pWindow ( )