private void NewCriteria_Closing(object sender, FormClosingEventArgs e)
{
ConditionForm C = Child.GetConditionForm();
if (C == null)
return;
// Hide closing New Criteria form, because setting "Child" to a new window
// will still display the old window below it until the new child closes.
Child.Visible = false;
Child = C;
Child.FormClosing += new FormClosingEventHandler(AddNewCriteria);
Child.ShowDialog();
}