IdP3 - Error message event flow override

[Petursson, Sigurdur]

I am detecting and mapping error codes in IDP3 
password-authn-config.xml. We now need to modify one of the scenarios to 
simply redirect the user to an external URL for a password change. Can 
someone provide an example of how this could be overridden in the most 
simple way possible:

     <util:map id="shibboleth.authn.Password.ClassifiedMessageMap">
         <entry key="ExpiredPassword">
             <list>
                 <value>data 532</value>
                 <value>data 773</value>
             </list>
         </entry>

-SP