How to display a div with scrollTop after certain pixels?

I have a (fixed) div that appears when the page scrolls down and reappears when the page scrolls up.
I need it to only appear (when moving down) 45px of the body. That is, while the user only rolls 44.9px does not submit and, of that, yes.

Here my example: http://jsfiddle.net/rcsxoqga/