thread Why do you need to have an apostrophe?
I can think of lots of ways of doing it with options A & B

Only other thing that occurs to me is to write a little VBA macro.
There's something you could adapt at th ebottom of the thread here:
permalink Because otherwise Foxpro fucks with the date upon import.
The macro in that thread seems massively complex.

Anyway for now (as I'm hoping not to use these spreadsheets) I've discovered that you can run the following in the Immediate window:

for each v in selection : v.value = "'" & v.value : next

which does the trick in a basic way.
permalink It did seem somewhat over long,
but maybe it was thorough and diligent or some shit.