SELECT ... FOR UPDATE

I am interested in using the SELECT ... FOR UPDATE feature but it doesn't
work quite the way I had hoped. If there is a better/different way of doing
this please enlighten me.

If I issue:

BEGIN;
SELECT * FROM atable WHERE atable.key = 10 FOR UPDDATE;

in one session and then issue the same commands from a 2nd session, the 2nd
session simply waits until the 1st session issues COMMIT or ROLLBACK. While
the 2nd session is waiting I am, apparently locked out. What I would like
is for the 2nd session to determine if the lock can be obtained and if not,
offer the user a choice of waiting or escaping from the SELECT. Is this
possible?

Using 7.0.3