Check for Valid Conference number in MeetMe

ASteriskNOW 1.7(*

Box is setup and working fine, and the only use for this will be Meetme conferences. Through exhaustive reading in this and other Asterisk forums, I have a solid working configuration with one small exception that I can’t seem to find a reference to anywhere, and I’m having a really hard time grasping the use of expressions, functions and variables in Asterisk.

I have set this up to terminate the H.323 trumk from my Avaya PBX directly to a context in extensions_custom.conf in order to have a single DID number that will allow callers to access multiple conference rooms.

There doesn’t appear to be a check for valid conference numbers in either meetme_additional.conf or the [ext-meetme] context in extensions_additional.conf.

I have found a line with an expression that checks to see if the CONFNUM is within a specified range of extensions, but I need it to check if the CONFNUM has been created in either the [ext-meetme] context, or in meetme_additional.conf.

My extensions_custom.conf…

exten => s,1,NoOp(Incoming OOH323, ${DNID})
exten => s,n,PlayTones(ring)
exten => s,n,Wait(7)
exten => s,n,StopPlayTones
exten => s,n,read(CONFNUM,conf-getconfno)
exten => s,n,GotoIf($[ $[${CONFNUM} >=100000] & $[${CONFNUM} <= 999999] ]?ext-meetme,${CONFNUM},1:)
exten => s,n,playback(conf-invalid)
exten => s,n,goto(ext-meetme-custom,s,5)

This works great except for the lack of true verification of a valid CONFNUM.
Any help or suggestions on where I can find a solution would be greatly appreciated