If in your search path for the compiler you have wxWidgets\include\wx then as in your program you hane #include <wx\app.h> the real searched file is wxWidgets\include\wx\wx\app.h, which is not correct.
In your global variable, simply use C:\wxWidgets. It is not necessary to add the include path because it is done automaticcaly by C::B.
Same problem in the project ..\..\wxWidgets\include\wx. It's redundant with the global definition (and \wx should be deleted).
In your project configuration, don't forget to add the global path by $(#WXWIDGETS)\include [or $(#WXWIDGETS.include)]: it's better than redefining the whole relative path (particularly if you move your project).