function calculate()
{
    $.get(  
        "../../ajax/wisselkoers_bereken.php",  
        {rnd: Math.floor(Math.random()*9999), munt_van: escape($("#munt_van").val()), munt_naar: escape($("#munt_naar").val()), aantal: escape($("#aantal").val().replace(",", "."))},
        function(responseText){  
            $("#resultaat").html(responseText);  
        },  
        "html"  
    );
}