javascript document.write breaking my page

I have this response.write on my page

function roundthecon() {
document.write(Math.round(exchRate*Math.pow(10,2))/Math.pow(10,2));
}

But it is re-writing my whole page and replacing it with the rounded number is there any other way of doing this without it re-writing my page?

Thanks

Jamie

UPDATE

Full javascript

if (exchRate != "") {

function roundthecon() {
var value = Math.round(exchRate*Math.pow(10,2)) / Math.pow(10,2);
$('.tablenotes > p > strong ').append(value);
}

function addCommas(nStr) {
nStr += '';
x = nStr.split('.');
x1 = x[0];
x2 = x.length > 1 ? '.' + x[1] : '';
var rgx = /(\d+)(\d{3})/;
while (rgx.test(x1)) {
    x1 = x1.replace(rgx, '$1' + ',' + '$2');
}
return x1 + x2;
}


            // When the document is loaded..
            $(document).ready(function(){


                    // Grab an array of the table cells
                    $('.evenprop table tr td:not(.title)').each(function(){

                            // Calculate the pound price
                            var v_euro = $(this).html();

                            if (v_euro != "N/A") {

                            var v_euro = v_euro.r开发者_JAVA技巧eplace(/,/g,'');
                            var v_euro = v_euro.replace(/\u20AC/g, '');
                            var v_euro = v_euro.replace(/£/g, '');

                            var v_pound = Math.round(v_euro / exchRate);
                            v_pound = addCommas(v_pound);

                            // Create a new span element for the pound


                            // Insert it at the end of the table cell

                            if (exchRate == <%= Session("xch_dollar") %>) {
                            $(this).prepend("$");
                            }
                            if (exchRate == <%= Session("xch_ntl") %>) {
                            $(this).prepend("X");
                            }
                            if (exchRate == <%= Session("xch_euro") %>) {
                            $(this).append("&euro;");
                            }

                            var o_span = $('<span/>').html(' <span style="font-weight:normal;" id="exchRate">(&pound;' + v_pound + ')</span>');
                            $(this).append(o_span);

                            }
                    });

            });

            }

function roundthecon() {
  var value = Math.round(exchRate*Math.pow(10,2)) / Math.pow(10,2);
  $('#some_element_id').text(value);
}

document.write is usually best to not use. It can do some strange things.

Try something like this:

function roundthecon() {
    document.innerHtml+=(Math.round(exchRate*Math.pow(10,2))/Math.pow(10,2));
}