Yes, this is VERY easy to do:
Imagine you have this DDI’s in your home/company:
So the macro is catching ANY call beginning with 555
Then it extracts the digits AFTER 555 (the exten:3 cuts the leading 3 digits)
So the voicemail is called like
“u” is “unavailable”, so you use this announcement - you could also use “busy” which is represented by a “b” instead of an “u”.
Add another line like
but put it in a context where calls from outside are not spawning, so no1 can dial in with “555-8500” to access your VM menue (or DO it if you actually WANT them to be able…)
8500 is the standard VM extension, prompting for the mailboxno. and a pin.