function scroller(s_block, s_scroller) {
	this.s_block = s_block;
	this.o_block = $(s_block);

	this.o_frame = this.o_block.parentNode;

	if (parseInt(this.o_frame.offsetHeight) < parseInt(this.o_block.scrollHeight)) {
		$(s_scroller).show();
	}

	// prepare block
	this.o_block.style.top = '0px';

	this.i_minLimit = parseInt(this.o_frame.offsetHeight) - parseInt(this.o_block.scrollHeight);
	this.i_maxLimit = 0;
}

scroller.a_instances = new Object();

scroller.setup = function(s_block, s_scroller) {
	scroller.a_instances[s_block] = new scroller(s_block, s_scroller);
}

scroller.up = function(s_block, s_callback) {
	scroller.a_instances[s_block].up(s_callback);
}

scroller.down = function(s_block, s_callback) {
	scroller.a_instances[s_block].down(s_callback);
}

scroller.stop = function(s_block) {
	scroller.a_instances[s_block].stop();
}

scroller.scroll = function(s_block) {
	scroller.a_instances[s_block].scroll();
}

scroller.prototype.up = function(s_callback) {
	this.stop();
	var i_distance = Math.abs(parseInt(this.o_block.style.top));
	var i_duration = Math.abs(i_distance) / 75;
	this.o_effect = new Effect.Move(this.o_block, {x : 0, y : i_distance, duration: i_duration, transition: Effect.Transitions.linear, afterFinish: s_callback});
}

scroller.prototype.down = function(s_callback) {
	this.stop();
	var i_distance = this.i_minLimit - parseInt(this.o_block.style.top);
	var i_duration = Math.abs(i_distance) / 75;
	this.o_effect = new Effect.Move(this.o_block, {x : 0, y : i_distance, duration: i_duration, transition: Effect.Transitions.linear, afterFinish: s_callback});
}

scroller.prototype.stop = function(s_callback) {
	try {
		this.o_effect.cancel();
	}
	catch(o_event) {
	}
}