96 530i computer code question

[killingjoker]

Just brought a minter of a 1996 530i V8 and am well pleased with it (and no doubt my local petrol station will be pleased to). However, daft question i know but, could anyone advise me on the code immobilzer option built into the trip computer. It says in the handbook that if i punch in a four digit code i can immobilize/alarm the car. Sounds good (as a secondary precaution to the other fitted fitted security device). But, is the four digit code any one that i care to pick, or is it predetermind set by BMW? I know, daft question, but anyone used this option?

thanks