How do I enter a code in an Nissan Micra '93 blaupunkt stereo. It currently says "---" and I can't seem to get it to register my attempts to enter the code?

Dai, May 2005

1. Switch on the radio.
2. Press any button on the unit. \\\"000\\\" is displayed.
3. Enter your personal code number by pressing station select buttons 1,2,3,4 the required number of times to display the code.
4. Press the tuning up rocker button to enter the code. The unit will unlock and teh radio/cassette will operate. If the wrong code number is entered, the display shows
\\\"---\\\". Wait ten seconds then enter the correct code.

Wishbone, February 2006