var phone_field_length = 0;
function TabNext(obj, event, len, next_field) {
    if (event == "down") {
        phone_field_length = obj.value.length;
    }
    else if (event == "up") {
        if (obj.value.length != phone_field_length) {
            phone_field_length = obj.value.length;
            if (phone_field_length == len) {
                next_field.focus();
            }
        }
    }
}


function blockNonNumbers(obj, e, allowDecimal, allowNegative) {
    var key;
    var isCtrl = false;
    var keychar;
    var reg;

    if (window.event) {
        key = e.keyCode;
        isCtrl = window.event.ctrlKey
    }
    else if (e.which) {
        key = e.which;
        isCtrl = e.ctrlKey;
    }

    if (isNaN(key)) return true;

    keychar = String.fromCharCode(key);

    // check for backspace or delete, or if Ctrl was pressed
    if (key == 8 || isCtrl) {
        return true;
    }

    reg = /\d/;
    var isFirstN = allowNegative ? keychar == '-' && obj.value.indexOf('-') == -1 : false;
    var isFirstD = allowDecimal ? keychar == '.' && obj.value.indexOf('.') == -1 : false;

    return isFirstN || isFirstD || reg.test(keychar);
}