Any Widget in Use Boolean

Hi,

I’m creating a custom theme for my blog, but I’m stuck at one spot. I’m trying to make my theme change it’s size if any widget is in use (i.e. if no widget is “on” it will be a smaller size than if a widget is “on”). Unfortunately I have not been able to find a way to know if a widget is in use. Is there a way for me to know if any widget is currently in use or not?

Thanks.