two grammatical questions

[virginiawang]

I often heard people say " at the expense of sb/sth". Can I say " in the expense of sb/sth" or " on the expense of sb/sth" ? I think I've also read them somewhere.
What is the phrase put in the beginning of a sentence that means, sth is bound to happen? " By all possibilities, I ..." Is that correct? If not, what is a better one?
" I stopped drinking milk for no thoer reason than my stomach not wanting it any more." Is it correct?

[Whifflingpin]

My two penn'orth, to start the ball rolling - pardon the mixed metaphors.

"I often heard people say " at the expense of sb/sth". Can I say " in the expense of sb/sth" or " on the expense of sb/sth" ?"
No.

"What is the phrase put in the beginning of a sentence that means, sth is bound to happen? " By all possibilities, I ..." Is that correct? If not, what is a better one?"
"No matter what, I.." "In all eventualities, I.." "In any case, I.." "Whatsoever king shall reign, I'll be the Vicar of Bray, Sir!"

" " I stopped drinking milk for no other reason than my stomach not wanting it any more." Is it correct?"

Commonly used but, I think incorrect - gerund takes the genitive or something. It should "my stomach's not wanting..." But few people would say that. ("my stomach's" meaning "of my stomach," of course, not "my stomach is.")
But it is clumsy, try "I stopped taking milk only because my stomach did not want it any more."