Hi and welcome.
The button on the steering whell is NOT a pairing button...
Do you have a similar one in the armrest?
Have you check if a bluetooth ULF box exists in your trunk (silver metal box, left side, a little below the MKIV unit), with a Bluetooth antenna (black plastic box, above MKIV)?
You can see all parts here: http://www.xoutpost.com/articles/all-...03-bmw-x5.html

Good luck