Press delay-arm 1 button,that's the 3rd button down right hand side.
Enter your current user code.
Press the delay-arm 1 button and the press button led should flash x3.
Enter your new code.
Press the delay-arm 1 button and the press button indicator led should flash x4 if new code is accepted.
That's the sequence for the early sl's and does differ for the later versions,so will need the model if it don't work.
We have accesss to all the manuals, but I can't give you one because it contains engineering info. Try it and get back to us.
e manno, November 2013