Certificate versus password

[Manuel Mollar]

Im am interested to get somethig like this in my .htaccess:

if HTTPS
  then
    allow if any certificate from my CA is presented
  else
    use classic user/password mechanism

Any idea?

-- 
        Manuel Mollar Villanueva
        Prof TEU depto informatica, UJI
        http://moon.act.uji.es
        mailto:[EMAIL PROTECTED]
        telf 964 72 8355