Someone

      <handler            class="org.eclipse.team.internal.ccvs.ui.actions.CheckoutWizardAction"            commandId="org.eclipse.team.cvs.ui.checkout">               <enabledWhen                     checkEnabled="false">                  <with                        variable="selection">                     <test                           property="z.ex.propertyTester.selection.count"                           value="1">                     </test>                  </with>               </enabledWhen>       </handler>