Use case example: change auto attendant (IVR) announcement from an external phone.
To override restriction of not being able to dial feature code 74 as external caller - we can use the following Custom application:
Principle of work:
We are using old recording file, in our example it will be "test": 
This is the original file that was recorded via Feature Code 74/Message recording option in Sounds menu (internally). The idea is to replace an existing file with new one. When the external caller dials a DID to hit the dial plan entry shown below - they will hear a "Beep" sound and the recording will immediately start. However you can add "Play sound" application to announce that your message will be recorded after "Beep" sound (optional).
To use this custom application, we need to build the following entry into the dial plan (matching a DID of course):
Where :
- (/rw2/var/lib/callweaver/sounds/00000/) - /path/to/file
NOTE: To verify the path (/path/to/file) - open your dialplan and use "Play sound" application and choose your message from Sounds menu:
/rw2/var/lib/callweaver/sounds/00000/ - is DEFAULT path and is used by DEFAULT . If you specifically place your recording in another folder - you will see /path/to/file differently. In this example file is stored at ~/00000/MusicOnHold/ folder .
- test:alaw - file name and format
- silence: seconds of silence allowed before the recording is stopped. If missing or 0, silence detection is disabled. ( In our case this is 0 )
- maxduration: maximum recording duration in seconds. If missing or 0, there is no maximum. ( In our case this is 0 )
- option: may be ‘skip’ to return immediately if the line is not up, or ‘noanswer’ to record even if the line is not up. ( In our case this is k )
Option parameters in 1.8:
- a: Append to existing recording rather than replacing.
- n: Do not answer, but record anyway if line not yet answered.
- q: quiet (do not play a beep tone).
- s: skip recording if the line is not yet answered.
- t: use alternate ‘*’ terminator key (DTMF) instead of default ‘#’
- x: Ignore all terminator keys (DTMF) and keep recording until hangup.
- k: Keep recorded file upon hangup.
- y: Terminate recording if *any* DTMF digit is received.
Note: the k option is used in the example dial plan entry above and should likely be used in your case so that the person calling in to change the announcement can simple hang up OR press the # key to terminate the recording of the new announcement.