removed certificate automatic check

hi,

we are using certificate login in the portal, and we have card readers in the keyboards so the portal can read the certificate from the cards and let us login. We want to know if the portal have any feathure to automatically check if the certificate is removed to logout the user. The idea is that when a user takes out the card "with the certificate" from the keyboard the portal could logoff the user. I suppose it could be with a periodic check of the certificate ... but i can´t find information about.

Thx,

Carlos