By adding Computer to the listening override prefix, and adding a command "Computer*" with "Start Listening" in first line, it does work but I still have to say Computer twice : "Computer" to override, and again "Computer" to execute the spoken command and to start listening.
If I don't enable the listening override prefix, the command "Computer*" is executed with one spoken"Computer", but then I can't say "Computer*, any command existing in my list" (like "Computer*, open doors"), cause that would mean using this :
Execute command, '{CMD_AFTER}' (by name)
,but the recognition of VoiceAttack is very poor in that case and it doesn't sucess to execute existing commands, it always tries to execute unexisting commands cause it doesn't understand what I am saying after "Computer*".