I want to know what the difference of this detour would be

Code:
DWORD WINAPI MYFUNCTION (int num1, file *filename, DWORD size)
{
       originalMYFUNCTION(num1, filename, size);
       num1 = NULL;
       filename = NULL;
       size = NULL;
       return NULL;
}

DWORD WINAPI MYFUNCTION (int num1, file *filename, DWORD size)
{
       return NULL;
}
Basically I want the function to return NULL and return null pointers and any values passed back to the main program as NULL. Which of these detoured functions is accomplishing that?