element fill rest of page after a top margin

On this fiddle: http://jsfiddle.net/TechplexEngineer/nFZ8e/1/

How could one get the blocks element to fill the rest of the sidebar?

Thanks, Blake

Edit: How can I make it so when I re-size the window the scrolled area remains s开发者_如何学Gotuck to the bottom. (No red shows beneath)

http://jsfiddle.net/TechplexEngineer/nFZ8e/7/

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Add overflow: hidden; to your sidebar, and set padding-bottom: 9999px; on your block-level element that you want to extend all the way down.

http://jsfiddle.net/nFZ8e/3/