Funky Button...what Does It Do?, Want information on a button. Options

[macbump]

Hi there, I am a new owner of a Sienna 2005 LE...enjoying it very much except for how much gas costs compared to the smaller cars I've always driven! ;-) Can't be avoided, growing family necessitated upgrade...

Anyhow, to the right of the area where the air conditioning buttons and what-not are, not very far from the front passenger airbag light that tells you if it is on or off or whatever, there is a flick-switch type button. It is round. It is *outside* the main climate control area, on the shiny black plastic. We are wondering what on earth it is for! It does not seem to be mentioned in the owner's manual and the previous owner (who I know personally) said she never found out what it was (she bought it new and it came with the button she says).

Anyone have any clue?

Thanks in advance!
Fio