function IsDate(txtDate)
{
    try
    {
        if (txtDate.length != 10)
        {
            return null;
        }
        else if
             (
                 isNaN(txtDate.substring(0, 2))       ||
                       txtDate.substring(2, 3) != "/" ||
                 isNaN(txtDate.substring(3, 5))       ||
                       txtDate.substring(5, 6) != "/" ||
                 isNaN(txtDate.substring(6, 9))
             )
        {
            return false;
        }
        else
        {
            return true;
        }
    }
    catch (e)
    {
        return null;
    }
}