Not really sure, but maybe this?
#ifdef xSCREEN_3.2
Screen3_2 myScreen;
#elseif defined(xSCREEN_5_0)
Screen5_0 myScreen;
#endif
Not really sure, but maybe this?
#ifdef xSCREEN_3.2
Screen3_2 myScreen;
#elseif defined(xSCREEN_5_0)
Screen5_0 myScreen;
#endif