I have a sheet which has only 3 input cells, but only one input cell is
required for a user in a given state. I've disabled the "move selection after
enter" function in tools/option/edit and when they enter a value and press
enter the active cell stays the same - which is what I want.

When I protect the sheet, the active cell jumps to the next unprotected
cell. How can I stop it doing that?