When you say the assistant has a group pickup key are we talking about a ringing group pickup key ie code 902?If so,then whenever his phone rings it's going to cause the assistant's phone to ring as well.The only way I see around it is with another port that you could ring the private line to and have a different ringing pickup key for that extension on the general managers phone.That could get a little messy however if there is voicemail involved.