<extension
         point="org.eclipse.ui.services">
       <sourceProvider
            provider="client.common.SessionSourceProvider">
           <variable
               name="sessionState"
               priorityLevel="workbench">
           </variable>
           <variable
               name="userRole"
               priorityLevel="workbench">
           </variable>
        </sourceProvider>
    </extension>

public WorkbenchWindowAdvisor createWorkbenchWindowAdvisor(IWorkbenchWindowConfigurer configurer) {
        // Save login information and cookies
        UserSession.getInstance().setEncodedUserName(Application.getEncodedUserName());
        UserSession.getInstance().setEncodedPassword(Application.getEncodedPassword());
        UserSession.getInstance().setCookies(Application.getCookies());
        UserSession.getInstance().setUserRole(Application.getUserRole());

        return new ApplicationWorkbenchWindowAdvisor(configurer);
    }

   <extension
         point="org.eclipse.ui.menus">
      <menuContribution
            allPopups="false"
            locationURI="toolbar:org.eclipse.ui.main.toolbar">
         <toolbar
               id="client.toolbar">

           <command
                  commandId="client.commands.toolbar.StopTransmit"
                  icon="icons/stop_sign.png"
                  label="Stop Transmitting"
                  style="push"
                  tooltip="Stop All Transmitting">
               <visibleWhen
                     checkEnabled="true">
                  <with
                        variable="userRole">
                     <equals
                           value="OPERATOR">
                     </equals>
                  </with>
               </visibleWhen>
            </command>
         </toolbar>
      </menuContribution>
   </extension>