Holsworthy's Somerfield store will close at 1pm on Wednesday, May 20 and remain closed for about a fortnight while changes are made, including installing a coffee and cakes café, and the staff retrained before it reopens as Waitrose.
With the Ruby Run taking place shortly after on June 14, Waitrose have agreed to be one of the sponsors of the event.
However, the race secretary, John Allen, is keen to hear from any individuals or firms willing to support the event as sponsors.