The CELGenUserEvent application allows you to instruct Asterisk to generate a user defined event with custom type name.
The event triggered is the
USER_DEFINED event as listed in the Asterisk 12 CEL Specification. The
userdeftype fields will be populated with data passed through the respective arguments provided to the CELGenUserEvent application.
Most CEL fields are populated by common channel data, so a unique function is not required to read or write that data on the channel. That channel data is already available via the CHANNEL function in currently supported versions of Asterisk.
Older versions of Asterisk had a unique CEL function. You can run "core show function CEL" to see if you have this function and display the help text.