Hangup handler for child channels

I have hangup handler and dial like _XXX => Dial(SIP/111&SIP/112&SIP/113)

My handler:

If user called at 112 handler will start only for SIP/112 channel and at cdr will write 3 records with MOS only for 112 even if 111 is answered.

Whats the best way to start handler for all child channels to write cdr?