This is best nokia mobile trick that will lock bluetooth of nokia mobile temporarily with a secret code.
Here is the trick.
Step 1: Turn the bluetooth ON (If it is turned OFF)
Step 2: Dial *#9990#
Nothing can be recieved or sent as well as device cannot be paired now.
Your work is done.
(To unlock bluetooth you need to Restart the phone.)
(This trick is not applicable for some symbian phones).