exten => s,n,Set(i=1)
exten => s,n,While($[${i} > 3])
exten => s,n,Set(i=$[${i} + 1])
exten => s,n,Set(CHANTOCHECK=${CUT(INBOUNDEXTENS,&,${i})})
exten => s,n,ChanIsAvail(${CHANTOCHECK})
exten => s,n,Set(CHECKED=${CUT(AVAILCHAN,-,${i})})
exten => s,n,Set(AVAILINBOUNDEXTENS=${AVAILINBOUNDEXTENS}&${CHECKED})
exten => s,n,EndWhile()