English is not my first language, but I do communicate a lot in non formal setting with UK born and bred very nice people. From where I come there a plenty of ways to say "This is not going to happen":
- it will happen on the 30th of February
- it will happen when shoes blossom
- it will happen when you see your back without a mirror
What will be nice and polite way to say that in front of a native speaker, showing her I have a deep interest in the language?