Q: locking some, but not all, properties of a cell

Folks,

Is there a way of locking the format of a cell, but not
the contents?

We have a shared yearly planner type spreadsheet in which
cells are coloured to indicate vacation, on course, off
sick, etc, and may also contain key letters to indicate
Early or late shifts.

I would like to allow anybody to input shift changes, but
reserve changes in vacation (cell colour) for the
administrator.

Thanks - Mike.