The cell format has be set as a Custom format mm/yy.

When entering dates into cells as mm/yy Excel interprets 12/96 as 01/12/96
(dd/mm/yy English format) BUT if you enter 12/06 it enterprets it as 12/06/07
and displays it as 06/07. IE Excel is interpreting 12/06 as dd/mm and
defaulting the current year.

Is there any way of getting excel to accept post 1999 years entered as yy?

This is part of an electronic questionnaire so the data entry has to be
completely idiot proof. I don't want to use yyyy or a format that needs the
days. Nor do I want to use macros or dummy columns if I can help it.

Any thoughts most welcome!