http://userscripts.org/scripts/show/65828

gistfile1.txt

// ==UserScript==
// @name           mint.com Net Total
// @description    Shows net total on Transactions tab.
// @include        https://wwws.mint.com/transaction.event*
// ==/UserScript==

window.addEventListener('load', function() {

    //add commas between every 3 digits
    var add_commas = function(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;
    }

    var sum_table_bank = function() { sum_total('account-table-all-bank'); setTimeout(sum_table_bank, 1500); }
    var sum_table_cash = function() { sum_total('account-table-all-cashonly'); setTimeout(sum_table_cash, 1500);  }
            
    var sum_total = function(table_id) {
        //add "Net Total" header 
        var totalTable = document.getElementById(table_id);
        if (totalTable == null) { return; }
        var tableHeaders = totalTable.firstChild;
        var tableHeadersArray = tableHeaders.getElementsByTagName('th');
        tableHeadersArray[2].innerHTML = 'Net Total';
        if (document.getElementById('net_total') != null) { return; }
        
        //add net total amount
        var tableValues = tableHeaders.nextSibling;
        var tableValuesArray = tableValues.getElementsByTagName('td');
        tableValuesArray[0].className = 'money';
        tableValuesArray[1].removeAttribute('colspan');
        var totalCash = tableValuesArray[0].innerHTML.replace('$', '');
        totalCash = totalCash.replace(',', '');
        var totalDebt = tableValuesArray[1].innerHTML.replace(',', '');
        totalDebt = totalDebt.substring(2);
        var netTotal = document.createElement('td');
        netTotal.className = 'money large positive';
        netTotal.id = 'net_total';
        netTotal.innerHTML = '$' + add_commas((new Number(totalCash) - new Number(totalDebt)).toFixed(2));
        netTotal.setAttribute('colspan', '3');
        tableValues.appendChild(netTotal);
    }

    setTimeout(sum_table_bank, 1500);
    setTimeout(sum_table_cash, 1500);
}, true);