jQuery.fn.vslide = function(){
	var v_container = jQuery('#slider-container #slider');
	var v_item_height = v_container.find('img').height();	
	var v_prev = jQuery('#slider-prev');
	var v_next = jQuery('#slider-next');
	var step = 0;
	var max_height = v_container.height()/2-v_item_height;
	
	v_prev.bind('click', function(){
	  if(step > 0){
		 v_container.animate({top: '-' + (step - v_item_height) +'px'}, 'slow');
	  	 step -= v_item_height; 
	  };	  
	});
	
	v_next.bind('click', function(){
	  if(step < max_height){
		 v_container.animate({top: '-' + (step + v_item_height) +'px'}, 'slow');
	  	 step += v_item_height; 
	  };	  
	});
	
}