To override restriction of 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. Idea is to replace existing file with new one.  When caller will reach to this entry of the dialplan - he will hear "Beep" sound and recording will start, however you can add "Play sound" application to announce that your message will be recorded after "Beep" sound. 

To do this, we need to build such row in the dialplan:

Record(/rw2/var/lib/callweaver/sounds/00000/test:alaw, 0,0,k)       | ORIGINAL VIEW: Record(filename:format[|silence][|maxduration][|option])

Where :