Sliding div after certain window scroll

I have this code (posted bottom) which I have put inside my template file for my home page. It locks my primary sidebar in place after the window scrolls down a certain amount. Problem is I want this to work with all my templates, now i can just paste this code into all my template files but I know there is a better way I just don’t know how. Should it go in the functions file some how?

<script>

  window.onload = function( ){
		jQuery( window ).scroll( function( ){ 

			var scroller_object = jQuery( "#sidebar-primary" );
			var num=305;

			if( document.documentElement.scrollTop >= num || window.pageYOffset >= num )
			{
				if( jQuery.browser.msie && $.browser.version == "6.0" )
				{
					scroller_object.css( "top", ( document.documentElement.scrollTop + 15 ) + "px" );
				}
				else
				{
					scroller_object.css( { position: "fixed", top: "285px" } );
				}
			}
			else if( document.documentElement.scrollTop < num || window.pageYOffset < num )
			{
				scroller_object.css( { position: "absolute", top: "590px" } );
			}
		} );
	}
  </script>