errors.add - how can i set the whole message?

Hi all. I'm using Rails 2.3.4. If i do this

myobj.errors.add(:password, "was incorrect")

then the password field gets an error, which comes out as "Password was
incorrect". However, i want the message to be "Please note that
passwords are case sensitive".

I know that i could add this message as an error on base, but i want to
add it to the password attribute so that the password field on the page
has the error markup wrapped around it.

Can anyone explain how i can do this? I'm stumped. I'm using I18n if
that helps.

cheers, max