Calling an event handler manually

I have an event handler method that's called directly as a standard method. That is, it's not only called when my event occurs but also just as a private method.

UtilStk.StkRoot.OnStkObjectAdded += new 
    IAgStkObjectRootEvents_OnStkObjectAddedEventHandler(TallyScenarioObjects);

private void TallyScenarioObjects(object sender)
{
    ...
}

Is it suitable to pass a null argument when calling this handler directly?

TallyScenarioObjects(null);