How to lock my Toshiba laptop keyboard when cleanup it?

I often eat when reading news online whether talking to my parents on Skype. As the issue, my keyboard ofttimes becomes dirty because of several potable drops. Whenever I want to clean my keyboard (almost each day) I want to holdfast it, so any pressed keys would have no effect (except special combination to open up it). How do I do that? Please, don't offer the answer with Windows lock screen feature. If there is no built-in feature, is there any code for Windows 7 which can do that?