Record Confbridge after 2nd ext add in conference!

I tried to use confbridge.
I have 2 extensions.
I put one extension in conference. the conference Room become its own extension number not predefined.
Then I originate call for another extension which should be add in that conference room.

this works fine. Now I want to Record call when 2nd extension enter in Conference Room.

I found on mailing list some one tried but failed.
Start/Stop recording in confbridge

My extension.conf entries as below:-

 exten => 1111,1,NoOp()
 same => n,goto(conference,1)
 exten => conference,1,NoOp()
 same => n,Set(CHANNEL2=${CHANNEL:4})
 same => n,ConfBridge(${CHANNEL2},,,sample_user_menu)
  exten => _2222XX.,1,NoOp()
  same => n,Set(EXTENNEW=${EXTEN:4})
  same => n,ConfBridge(${EXTENNEW},,,sample_user_menu)

I tried Asterisk-java library, MonitorAction & StopMonitorAction. Even I use
confbridge record start Conference Name
confbridge record stop Conference Name
At time of dial 2nd extension to add conference & hangup of it from conference.

But I need to learn how to do it by dialplan only!
Need help.

There is no dialplan application that will do this.

Your only approach to do this in the dialplan would be to use the Originate dialplan application to spawn a Local channel to an extension that calls Record on the Local channel, then place the other half of the Local channel in the ConfBridge with the two real channels. You could use a special user profile for the Local channel that would prevent any notifications (beeps, etc.) from being played when the Local channel enters.

The suggestion by @mjordan is the best approach, another way would be using local channel when adding the second extension to the conference and chanspy with the r option to record the session