You can look up most script conditions and commands in the docudemons - a necessary tool for doing any scripting. Be warned that some of the descriptions in that file are incorrect and some information is missing. It is quite useful as a general guide but always be sure to test everything for yourself.
The syntax for send_character_off_map is simply:
Code:
send_character_off_map character_label_1
You can also use character name, but I strongly recommend using unique labels instead of names wherever possible.