如何在wcf客户端中更改时间戳安全头？

<configuration>
  <system.serviceModel>
    <bindings>
      <wsHttpBinding>
        <binding name="MyBinding">
          <security mode="Message">
            <message clientCredentialType="Windows" />
            <timestamp enabled="true" />
          </security>
        </binding>
      </wsHttpBinding>
    </bindings>
    <client>
      <endpoint address="http://example.com/MyService.svc"
                binding="wsHttpBinding"
                bindingConfiguration="MyBinding"
                contract="MyService.IMyService" />
    </client>
  </system.serviceModel>
</configuration>