Can I use Massar money to attend the Chinuch convention? I would be losing money by not working those two days in the summer plus my salary in the summer is less then the year?
P.S. this has nothing to do with the fact that you are losing money while attending the convention.
Maaser money can be used to pay for non-obligatory Mitzvos and this is included.
P.S.S. This is not an endorsement for any convention or organization.