dropdownmenu to backing bean save state

[codecoaster]

I have an advanced search form and have set up a dropdownmenu to take the operation to be performed on the search date. eg. On-Before-After etc.
Here is the code which seems to work as intended and the dateOp value is being changed in the backing bean.
here is the code for the menu:

<h:column id="ddcol">
 <h:form id="ddform">
 <!--plan:when a date operation is selected it stores the value in dateOperation-->
 <!--The value in dOp should be rendered with value of dateOperation-->
 <!--When the search button is clicked dateOperation etc will be passed to a method in backing bean-->
 <rich:dropDownMenu id="ddmenu" submitMode="ajax" binding="#{«asInstanceVar()»CrudBacking.dateOp}" onitemselect="render='form.dOp'" immediate="true" >
 <f:facet name="label">
 <h:panelGrid id="pg" cellpadding="0" cellspacing="0" columns="2" style="vertical-align:middle">
 <h:graphicImage value="/images/icons/date_go.png" style="border: 0px"/>
 <h:outputText id="t" value="Date" />
 </h:panelGrid>
 </f:facet>
 <rich:menuItem value="On" reRender="form.dOp" icon="/images/icons/flag_blue.png" >
 <f:param id="On" name="id" value="On" />
 </rich:menuItem>
 <rich:menuItem value="Before" icon="/images/icons/resultset_previous.png" >
 <f:param id="Before" name="id" value="Before" />

 </rich:menuItem>
 <rich:menuItem value="After" icon="/images/icons/resultset_next.png" >
 <f:param id="After" name="id" value="After" />

 </rich:menuItem>
 <rich:menuItem value="Between" immediate="true" icon="/images/icons/tag.png">
 <f:param id="Between" name="id" value="Between" />
 </rich:menuItem>

 <rich:menuItem value="Any" >
 <f:param id="Any" name="id" value="Any" />
 </rich:menuItem>
 </rich:dropDownMenu>

 </h:form>
 </h:column>
 <h:column id="outCol" styleClass="header">

 <h:outputText id="dOp" render="true" ajaxRendered="true" name="dateOp" style="font-weight:bold" immediate="true" value="#{«asInstanceVar()»CrudBacking.dateOp}" />
 </h:column>

This is the code in the backing bean:

public void setDateOp(String s){
 FacesContext ctx = FacesContext.getCurrentInstance();
 this.dateOp = (String)ctx.getExternalContext().getRequestParameterMap().get("id");
 System.out.println("setting date op from string: "+dateOp);
 }

The code to get the dateOp string from the bean is:

public String getDateOp(){
 if(dateOp==null){dateOp="Any";}
 System.out.println("getting date op: "+dateOp);
 return dateOp;
 }

I have the dateOp variable initialised as:

public String dateOp="On";

The problem is the value returned from the bean is always 'Any'
Any help with this would be great as i have been stuck on this for over a week!
Thanks in advance
Codecoaster