My system date format is yyyy-MM-dd (2015-07-11).

In excel, I want to be able to enter a date as d-m-yy (11-7-15).
BUT
If I enter 11/7, I get 2015-11-07.
if I enter 11/7/15, I get 2011-07-15

How do I go about it without changing my system date format?

win xp sp2 , office xp.

thx