SelectOneList

Front-end
#1

eu gostaria que o selectonelistbox fizesse assim: que um parametro quando selecionado clickando num button passase para outro selectonelist box.
eu tentei mais ainda naum conseguir

<h:selectOneListbox id="selOneList" size="5" style="width: 123px" value="#{ususario.nome}">
  			<f:selectItem  itemValue="Alan1 " itemLabel="Valor1" id="a1"/>
  			<f:selectItem  itemValue="Alan2 " itemLabel="Valor2" id="a2"/>
  			<f:selectItem  itemValue="Alan3 " itemLabel="Valor3" id="a3"/>
  			<f:selectItem  itemValue="Alan4 " itemLabel="Valor4" id="a4"/>
  			<a4j:support id="a4jinte" reRender = "selecttwolist" event=" onclick " />
		</h:selectOneListbox>
	<h:form>
               <a4j:commandButton  id="a4it"value="->" reRender="selecttwolist" onclick="selecttwolist">
               </a4j:commandButton>
               <a4j:commandButton value="<-" reRender="selOneList"onclick="selOneList">
               </a4j:commandButton>
        </h:form>         
               <rich:separator></rich:separator>  <br />
               <h:selectOneListbox id="selecttwolist" size="5" style="width: 123px"value="#{ususario.nome}">
                      <a4j:support id="a4itsnd" reRender="selOneList" event=" onclick " ></a4j:support>
                 </h:selectOneListbox>
#2