This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
Paul's post notwithstanding, the answer is "you can't, unless class B helps you out." Java is deliberately designed to make what you describe impossible, unless class B provides a "backdoor" so that A's "doIt" can be called independently of the override.