function isNumberKey(e)
{
    if (window.event) // ie
    {
        charCode = e.keyCode;
    }
    else if (e.which)
    {
        charCode = e.which;
    }
    else
    {
        return true;
    }

    if (!charCode)
    {
        return true;
    }

    if (charCode > 31 && (charCode < 48 || charCode > 57))
    {
        return false;
    }

    return true;
}