Rick Colley, 62, from Burgess Hill, said he will need to do at least 33,000 steps each day in March, which could take about four to five hours on top of his normal work day.
Rick, who lives with his wife and has four children in Mid Sussex, has spent much of his life policing the district.
“I know the area very well,” he said, adding that he was born in Canada but his family moved to Haywards Heath in 1963 when he was four.
“I’ll be walking around Burgess Hill, Haywards Heath, Hurstpierpoint and possibly Hassocks,” said Rick, who encourages residents to wave if they see him in his MND Association shirt.
Rick started working for Sussex Police in 1978 and retired from being a police officer in 2008 to become a prosecution caseworker.
After five years he became a specialist caseworker with the Serious Collision Investigation Unit at Haywards Heath.
March will mark Rick’s 521st month – more than 43 years – with Sussex Police.
He said he is passionate about fairness and justice and that he has had a fulfilling career helping people, sometimes in very serious circumstances.
Rick said he had raised money for Crohn’s & Colitis UK when he retired from being an officer and decided that raising funds for the MND Association would be best this time.
His grandmother Marjorie Warden was diagnosed with MND in 1988 and died from it that same year.
As a rugby enthusiast, Rick was also inspired by the bravery of rugby players Doddie Weir and Rob Burrow, who have both bee diagnosed with MND.
“MND is not choosy about who contracts it,” said Rick, adding that the ‘million steps’ idea came to him after his son gave him an old Fitbit watch.
Rick is looking forward to the challenge but said it might be tough on his hips and that he will have to work hard every morning to get moving again after the previous day.
“If I time it right I should be finished early evening most days, but I don’t know,” he said, adding that he will walk everywhere until he hits his daily target, regardless of how long it takes.
People can donate at www.justgiving.com/fundraising/Richard-Colley4.
Motor neurone disease is a fatal and rapidly progressing condition that affects the brain and spinal cord.
It attacks the nerves that control movement so muscles no longer work and it kills a third of people who get it within a year.
The MND Association focuses on improving access to care, research and campaigning for those affected by MND in the UK.