Certificate revalidation for senstive url

[Charan Teja Sri Rama]

I am working on an application which integrates portal with an applet. The user logs into the portal using a certificate and credentials.Then the user selects an url from the portal which leads to my applet. After selecting the url and before the applet is displayed, I need to re authenticate the user by re-selecting the certificate. Please help me with the required information on fulfilling this requirement.