I want to render a part of a menu only if a value is true, but I cant get it to work. Any idea how to achive this? Does EL work with the params?

<rich:contextMenu attached="false" id="contextMenuId" submitMode="server">
 <rich:menuGroup value="#{msg.global_customer} {customer}" icon="/app/images/customer.gif" disabled="{customerExists}">
 <rich:menuItem icon="/app/images/edit.gif" ajaxSingle="true" value="#{msg.global_button_alt_customerDetails}" action="customerDetails" >
 <a4j:actionparam name="contract" assignTo="#{customer.currentCustomer}" value="{dealerCode}{customer}" actionListener="#{customer.loadCurrentCustomer}"/>
 </rich:menuItem>
 <rich:menuItem icon="/app/images/axapta.gif" ajaxSingle="true" value="#{msg.menu_axapta_outstandings}" action="goOutstandings" >
 <a4j:actionparam name="contract" assignTo="#{customer.currentCustomer}" value="{dealerCode}{customer}" actionListener="#{customer.showOutstandings}"/>
 </rich:menuItem>
 </rich:menuGroup>
</rich:contextMenu>

<rich:componentControl event="onRowDblClick" for="contextMenuId" operation="show">
 <f:param value="#{data.contractDealerCode}" name="dealerCode"/>
 <f:param value="#{data.contractNo}" name="contract"/>
 <f:param value="#{data.contractChassisNo}" name="chassis"/>
 <f:param value="#{data.contractCustomerNo}" name="customerExists"/>
</rich:componentControl>