Am I responsible for my Attorney's mistake?

[suhanal]

My attorney made a mistake in the calculation of the total amount on my settlement, for example, he said that I should receive $1000.00 in total, broke it down saying $800.00 in bank account and $100.00in retirement fund...That total $900.00 NOT $1000.00 so at the end of the divorce, I received$900.00 instead...How can I claim the remaining $100.00 when I have already signed the settlement and the agreement and finalized everything???