How to create a timer which can run after screen has been saved?

Is there any codes can run after screen has been saved()?
Is thera a way.

P.S. I try to write following codes,
CCDirector::sharedDirector()->getScheduler()->scheduleSelector(schedule_selector(MTimer::update), this, 59, false);
but when screen is saving, it can not work.(Test in android 2.3)

Thanks.