(defun INVERSENORMAL (OBJ)
  (if(setq OBJ(cond
                ((=(type OBJ) 'VLA-OBJECT)OBJ)
                ((=(type OBJ) 'ENAME)(vlax-ename->vla-object OBJ))
              )
     )        
    (vla-transformBy
      OBJ
      (vlax-tmatrix '((1. 0. 0. 0.)
                      (0. 1. 0. 0.)
                      (0. 0. -1. 0.)
                      (0. 0. 0. 1.)
                     )
      )
    )
  )
)
(defun C:INVERSENORMAL()(INVERSENORMAL(car(entsel))))
(princ
  (strcat
    "\n\n"
    "\n[DT]INVERSENORMAL : Invertiert die Normale eines Objektes"
    "\n==================="    
    "\n(C) Thomas Krüger 2010 "
    "\nwww.cad-od.de / www.d-tools.eu / E-Mail: tk@cad-od.de"
    "\nBefehlszeilenaufruf : INVERSENORMAL\n"
  )
)
(princ)