[Asterisk-Users] Multiple multiline sip phones ringing.

[C F]

how would one dial multiple multiline sip phones (cisco 7960) and
making sure that all the phones ring on the next available line
appearance?
I'm currently using the local channel to accomplish this but I'm
having some trouble. Here is the configs:
each cisco 7960 phone has six registrations in sip.conf, 1XX1 thru
1XX6, normaly when an extension is dialed the following happens:

exten => 101,1,Macro(stdext,${EXTEN})
[macro-stdext]
;arg1 = ${EXTEN}
exten => s,1,Diall(sip/${ARG1}1,45,r)
exten => s,2,Goto(s-u,1)
exten => s,102,Dial(sip/${ARG1}2,45,r)
exten => s,103,Goto(s-u,1)
exten => s,203,Dial(sip/${ARG1}3,45,r)
exten => s,204,Goto(s-u,1)
exten => s,304,Dial(sip/${ARG1}4,45,r)
exten => s,305,Goto(s-u,1)
exten => s,405,Dial(sip/${ARG1}5,45,r)
exten => s,406,Goto(s-u,1)
exten => s,506,Dial(sip/${ARG1}6,45,r)
exten => s,507,Goto(s-u,1)
exten => s-b,1,Voicemail(b${ARG1})
exten => s-u,1,Voicemail(u${ARG1})

when I want to ring mutiple phones this is what I do:

[rollover]
exten => _1XX,1,Dial(SIP/${EXTEN}1,45,r)
exten => _1XX,102,Dial(SIP/${EXTEN}2,45,r)
exten => _1XX,203,Dial(SIP/${EXTEN}3,45,r)
exten => _1XX,304,Dial(SIP/${EXTEN}4,45,r)
exten => _1XX,405,Dial(SIP/${EXTEN}5,45,r)
exten => _1XX,506,Dial(SIP/${EXTEN}6,45,r)

[default]
exten => 160,1,Dial(Local/101 at rollover&Local/102 at rollover)

the problem is that if:
1. A phone is not registered the dial fails.
2. It doens't hand back nicely to exten 160,2 in default (it first
waits for the timeout)