Transfering call to two phones after timeout


we have small office with two support guys. So our support number is simultaneously ringing two desk phones, after dial timeout i wanted to dial theirs cell phones.

I tryed this extension setting:

exten => _999111111,1,Set(CALLERID(name)=Hotline) exten => _999111111,2,Dial(SIP/999111112&SIP/999111113,10) ; desk phones exten => _999111111,3,Set(CALLERID(number)=999111111) exten => _999111111,4,Dial(SIP/777123123@111.122.308.26&SIP/777123124@111.122.308.26) ; cell phones exten => _999111111,5,Congestion exten => _999111111,6,Hangup

With one cellphone it is working ok, but if i try both phones i hear only silence after first dial timeout even if it rings on cellphones. Exist working solution for this? (i have asterisk 1.4.11)