Maximum of inbound channels to specific number

Hi Guys

I am wondering if anyone out there knows of a configuration that will allow me to set a maximum of 15 inbound channels to a specific number, and if it goes above 15 to then play a message from a .wav file or something similar then have the call disconnected? Any assistance would be greatly appreciated.

core show function GROUP_COUNT

“A specific number” is an “extension” in Asterisk terminology.