MS Access Query to update
Use IN clause as following

UPDATE Packet SET Packet.MSGState = 'P'
Where (MSGState &lt;&gt; 'R' and  MSGState &lt;&gt; 'D') and
Packet.MSGTO IN
(Select  MSGTO.MSGTO
From MSGTO
Where  MSGTO.Selected = 'Y' and MSGTO.Selected IS NOT NULL )