I usually use the scheduler for this, which you can use to call a method at fixed time intervals, like this:
this->schedule(schedule_selector(Game::UpdateTimer),1.0f);
in this case it calls 'Game:UpdateTimer' once a second. In update timer you'd just reduce your counter by one, and when it's reach zero stop the timer like this:
this->unschedule( schedule_selector(Game::UpdateTimer));
and add a method underneath to be called
void Game::UpdateTimer(float dt)
{
}