how to know argument name with which a function of extended c called

[rahul]

Hi,
  i need to write a 'c extension function' in this function i need to
change argument value with  which this function called.
  ie,
         if a python code like
            import changeValue as c
            arg="old value"
            c.changeValue(arg)
            print arg

 then it print "new value"

 i write code like this..

static PyObject *changeValue(PyObject *self,PyObject *args){
        PyObject *sampleObj, *m ;
	char *argName;

      if (!PyArg_ParseTuple(args, "O", &sampleObj)){
                return NULL;
      }

   m = PyImport_AddModule("__main__");
   PyObject_SetAttrString(m, argName, "new value");
   return Py_BuildValue("");
}

But for this i need to know the argument name with which this function
called .
Is this possible to know argument name in extended c function? if yes,
than how i can do it???