how to correct an error in an divorce agreement (years old)?

I had my then hu*****and signed to waive my 401K in 2004.  By the time we were in the divorce process in 2007, I forgot that he waived my 401K (I was at emotional and stressed out condition and could not think well).  In the agreement he used my 401K to exchange a real estate property.  Recently I remembered about the waive and think it is very unfair to me.  Can I file a correction to the agreement?  Is it possible to dig out the notarized signature from my previous employer (or county/city)?  My then 401K is now a rollover IRA.  It seems a little complicate, but I want fairness and justice.  Thanks for any input.