Blocking voice clip (voice chating) in windows live messenger

Does anybody knows how to block using voice clip from windows live
messenger. My daughter knows that im logging all her chating text. Her
workaround is to use the voice clip now (wise girl!). I found how to
configure my router to get the voice call and web conferencing out of use
but the voice clip is still working! Wich port number i have to block?
.