Advance Alerts - Only if Acknowledged

Hi,

I am trying to create an Advance Alert that will only trigger when a node is Down and also when it is Not Acknowledged.

I have setup two advance alerts, identical except that one sends an email and the other does not.  The one that sends the email is set 30 mins polling.

- Alert 1 = Just event log, no email, timer = 0

- Alert 2 = Event log + send email, timer = 30 (check alert every 30 mins).

With the above, I make sure that I go to Alert tab and acknowledge the down event after Alert 1 triggers as my intention is that Alert 2 will not trigger.  However Alert 2 always trigger and I end up with the email being sent.

I have tried below as a SQL filter in the advance alert but it does not work.  Does anyone have any suggestions?

Thanks very much.

SQL

inner join AlertStatus on Nodes.Caption = AlertStatus.ObjectName WHERE ((Nodes.Status = '2') AND ( AlertStatus.Acknowledged = 0)