Windows 7: Automatic Definition Updates for MSE

I have read that you can use windows update to automatically update the definitons on MSE. Is this true? If so how do I get it to work? I have it set to install updates everyday at a certain time but it never seems to do so. Say my pc is not on during that time when I do turn it on will it then check for updates? And then when I open MSE and look at when the last time the definitons have been updates it is always the last time I did it manually. Basically can someone help me understand this whole process, and is there a way to get it to update automatically? Thanks

MSE update faqs:
MSE Definitions/Signatures Update FAQ

Thanks for your help