How to disable a custom field in a certain week day

[Anne Bione]

Hello guys!

I'm the admin of http://jazzb.net/. In this website we have 3 custom fields created with magic fields: "Cardapio" (menu), "Shows" (concerts) and "Fotos" (Photos). 

I'm struggling to find a way to disable "Cardapio" every sunday because, well, the club doesn't open on sundays so there's no special menu of the day. So every sunday we get an empty <div> without a menu which is not appropriate as you may predict.

Sorry if this sound way too specific and/or if I sound like I want someone to do the work for me, it's not the intention, but can someone help?

Just FYI, I'm not the original developer of this website, so I'm kind of a newbie with Magic Fields.

Thanks in advance!