Trigger event on specific scroll location

I want to trigger a specific event on a predefined scrollTop value.

I tried:

$(window).scroll(function () {    sym.$("scrpst").html($(window).scrollTop())


var nerde = sym.getVariable("scrpst");


if ( nerde == 200 ){
sym.$("floatmenu").show();
}else if ( nerde == 400 )
sym.$("floatmenu").hide();
}


})

where am I doing wrong?

Thanks in advance.