Well, i tried the battery replacement DIY but no luck, the remote locking still wont work. I'm trying to look at all my options before i order one through BMW ($580 here in Australia). Apart from going direct through BMW do i have another options?

Would this key work if i followed what the description says?
BMW KEY REMOTE TRANSPONDER SUITS X5 Z3 Z4 3 5 7 SERIES - eBay, Other Car Parts, Accessories, Car Parts, Accessories, Cars, Bikes, Boats. (end time 24-Aug-09 23:34:07 AEST)

Appriciate all the help guys.

Mike