(よ)うものなら

Usage

Used to express 'something that shouldn't be happened and the unfavorable situation when it happens'

言おう + ものなら

彼女との記念日を忘れようものなら、１週間は口を利いてもらえないだろう If I were to forget our anniversary, she probably wouldn't talk to me for a week

浮気がバレようものなら、離婚は免れないだろう If my affair were to be discovered, divorce would be inevitable