I have problem with implementing simple usecase in seam and richfaces.

I have two 'screens', every screen is managed by another ejb bean.

Description :
1) I want visit second screen from first screen
2) fill some data in second screen and then ...
3) i want go back to the first screen...
4) where will be still previously filled data and with data from second screen.

first screen xml configuration :
  
 
 <begin-conversation join="true" />
  <navigation from-action="addButtonInFirstScreen">
        <redirect view-id="/secondscreen.xhtml" />
  </navigation>


second screen xml configuration :


  <navigation from-action="iWantGoBackToFirstScreen">
        <redirect view-id="/firstscreen.xhtml">
             <param name="passedFromSecondScreen" value="#{secondScreenEJBBean.data}"/>
        </redirect>
  </navigation>

With this configuration, when i go back into first screen - all previous form datas are away !
and even more parameter 'passedFromSecondScreen' is blank.

Whats wrong here ? I am seam newbie.

Thank you your tips i will tell you more is some informations are missing.