Probably the only way to achieve this is to dismantle the cooker far enough to remove the time - as if you were replacing the timer - then (Carefully) remove the PCB and display from the casing of the timer. Then you should be able to remove the offending piece of button, clean all the button holes of collected congealed cooking residue, reassemble and then find a very large ladle to repeatedly beat said DIY challenged household member.
Do go carefully
Do think before taking each step
Do make notes of what screws and wires go where ON A BIT OF PAPER. - don't trust memory.
Make sure you know how to reset the timer and get the cooker into manual mode when it is powered back on. (RTFM)
And it is kinda obvious - make sure the cooker is isolated first!
XXX, April 2016
