asterisk users - Jun 2008 - How to set name of call wav recording file in outgoing/call file?

When I mv a file to /var/spool/asterisk/outgoing in order to place a
call from a user extension that will always be recorded, what
parameter do I set in the call file in order to specify an exact name
for the wav file?

This is on Trixbox and at the moment I'm considering setting an extra
variable and calling through a new calling context that reads this
variable and sets the recording name.

-HJC