populate a drop down based on the value of another drop down which are in a data table

[Vaibhav Mittal]

I am stuck with something. I have a data table which contains two drop downs. One is populated based on the value of the other. The problem is- in each row, the dependent drop down(if i may call it that) is populated based on the value of the first drop down that is selected for a particular row.

  

 <rich:dataTable binding="#{StudentListNotAllocated.uiDataTable}"   width="100%"  styleClass="TableBorder Bluelightest"        value="#{StudentListNotAllocated.studentList}" var="iter"     id="dtTable"  >



<rich:column headerClass="borderHeadingTRB  trCursor facet"  width="20%">
                  <f:facet name="header" >
                         <h:outputText value="Pickup Point"/>
                     </f:facet>
                                         
                           <h:selectOneMenu styleClass="fontStyledAjax"  value="#{iter.MDropAt}" style="width:150px;" >
                                
                               <a:support oncomplete="callCustomChoose(this);" event="onchange"                         action="#{StudentListNotAllocated.populateRouteListForChosenPickupPoint}" reRender="sltroutenumber"/>

                                <f:selectItem itemLabel="#{msg.Select}" itemValue="0"/>
                                <f:selectItems value="#{StudentListNotAllocated.MDropAtList}"></f:selectItems>
                            </h:selectOneMenu>
</rich:column>

<rich:column headerClass="borderHeadingTRB  trCursor facet"  width="10%">
                <f:facet name="header" >
                         <h:outputText value="Route No."/>
                 </f:facet>

                 <h:selectOneMenu id="sltroutenumber" onchange="callCustomChoose(this);" styleClass="fontStyledAjax"     value="#{iter.MRouteNumber}" style="width:80px;">
                                <f:selectItem itemLabel="#{msg.Select}" itemValue="0"/>
                                <f:selectItems value="#{StudentListNotAllocated.MRouteNumberList}"></f:selectItems>
                   </h:selectOneMenu>
</rich:column>
</rich:dataTable>

As you can see, the route number drop down has to populated based on the selection of the pickup point. I am able to get the pick up point id of the selection that is made on the first drop down(which is pickup point) but i am unable to catch hold of the corresponding drop down for route. Any ideas or thoughts would be very helpful. Thanks.