you dont need a cab
heres what you do
go into settings > Lock
tick where it says promt if the phone is not used for >> and change that to 0 minutes
then set ur self a 4 digi pin
now when either u press the power button to wake ur phone it will take you to the locked screen.
how ever when you slide the lock you will be promted by for the 4 digi pin you setup.
Sorry mate if you wanted it to lock but not promt you for a pin- i dont belive you can do that with the default options on WM.
good luck in finding another solution if the above does not help keep this thread updated, others may find it usefull
GALAXY NOTE 10.1
NETWORK: Got em all baby