function definedkeys_only(e, keys)
{
    switch (e.keyCode) {
        case 8:
        case 9:
        case 13:
        case 37:
        case 38:
        case 39:
        case 40:
        case 46:
            return true;
            break;
    }

    var re = new RegExp(keys);

    return re.test(String.fromCharCode((e.which) ? e.which : e.keyCode));
}