There can be defined conditions, for which a change to the next panel in the installation wizard is allowed.

This can be achieved by a nested definition into the panel definition od the installer descriptor:

<panels>
    ...
    <panel classname="TargetPanel">
      <validator classname="com.izforge.izpack.installer.validator.ConditionValidator"/>
    </panel>
    ...
</panels>

There can be used built-in or user-defined data validators.